Prowlarr Troubleshooting: Diagnose Failed Indexers and App Sync

Rights and lawful use: Configure Prowlarr only for indexers, categories, and searches you are authorized to access. Connecting Sonarr or Radarr does not grant permission to acquire or share media, so keep every automated query and downstream import within the rights and service terms that apply to you.

Quick Answer

Start at the first boundary that fails: test the indexer in Prowlarr, test the Sonarr or Radarr app connection, confirm the synced indexer in that app, then run an interactive search and read its rejection reasons. Back up Prowlarr and record the current sync level before changing anything. Do not delete and recreate a working indexer first; that destroys the state needed to distinguish credentials, URL base, categories, rate limits, and sync ownership.

Evidence status: This revision was reconciled with current Prowlarr, Servarr, and API documentation on August 24, 2026. TechGeeks did not connect a live indexer, create the planned failure canaries, measure recovery time, or capture current UI/log evidence. Commands and outputs below are an unperformed diagnostic runbook, not reported lab results.

Who this is for: This guide is for operators whose indexer passes or works in Prowlarr but fails, disappears, or behaves differently in Sonarr or Radarr. The goal is to locate one failing layer, preserve working settings, repair the narrow cause, and prove the request path end to end.

Match the Symptom to the Failing Layer

Symptom	First owner to inspect	Proof to collect	Do not do first
Indexer Test fails in Prowlarr	Provider-to-Prowlarr connection	Test error, UTC time, Prowlarr health event, matching application log context	Resync every application
Prowlarr Test passes, app Test fails	Prowlarr-to-Sonarr/Radarr connection or callback URL	App URL, URL base, container DNS, TLS result, API-key rotation state	Replace the indexer definition
App Test passes, indexer is absent or drifts	Sync profile, tags, categories, or sync ownership	Sync level, app tags, indexer tags, supported categories, before/after field values	Edit a Full Sync-managed field only in Sonarr/Radarr
Indexer exists and tests, but searches return nothing	Capabilities/categories or the provider query	Prowlarr search, app interactive search, expected category, history entry	Enable every category
Results appear but are not grabbed	Sonarr/Radarr decision rules	Interactive-search rejection reason, profile, custom format, size/language rule	Blame Prowlarr for an intentional rejection
Health warning appears after repeated tests	Rate limit, authentication, provider availability, DNS, or TLS	First error, response class, retry count, provider limit/term, recovery time	Loop Test or bypass a provider control

Before You Start: Preserve the Failure

• Use an authorized synthetic or open-licensed search target. Do not publish provider names, account details, search history, or media titles.
• Record the Prowlarr, Sonarr, and Radarr application versions and UTC time without assuming the latest release is installed.
• Capture the current Prowlarr app entry: internal URL, URL base, sync level, sync profile, tags, and selected categories. Never capture the API key value.
• Record whether the affected indexer is enabled for RSS, automatic search, and interactive search in the target app.
• Back up Prowlarr's app-data directory and save the Compose file or package version before changing ownership or updating.
• Change one variable at a time. A canary app or disposable Prowlarr instance is safer than breaking production deliberately.

Rights note: Prowlarr organizes indexer access. Only add indexers and categories you are allowed to use, and remember that Prowlarr does not override the rules or terms of any service.

The Docker backup sequence below assumes the published stack path. Adjust it to your deployment and use restricted, preferably encrypted storage. It validates the source files before stopping Prowlarr and installs an exit trap so an archive failure does not leave the service down.

set -Eeuo pipefail
cd /opt/media-stack
BACKUP_DIR=/secure-backups
STAMP=$(date -u +%Y%m%dT%H%M%SZ)
test -d prowlarr/config
test -r compose.yml
test -r .env
sudo install -d -m 0700 "$BACKUP_DIR"

trap 'docker compose start prowlarr' EXIT
docker compose stop prowlarr
sudo tar -C /opt/media-stack -czf \
  "$BACKUP_DIR/prowlarr-$STAMP.tgz" \
  prowlarr/config compose.yml .env
docker compose start prowlarr
trap - EXIT

docker compose ps prowlarr
docker compose logs --tail=100 prowlarr
sudo test -s "$BACKUP_DIR/prowlarr-$STAMP.tgz"

Example expected state (not observed): Compose shows the Prowlarr service running, and its startup log has no database-migration, permission, or bind error. This only proves the service restarted; it does not prove the archive can be restored.

Know Which Application Owns Each Setting

Prowlarr centralizes indexer definitions and synchronizes compatible entries outward. Sonarr and Radarr still own media monitoring, quality profiles, custom formats, root folders, download clients, completed-download handling, imports, and final acceptance or rejection. That ownership boundary determines where a repair belongs.

1. 1. SourceIndexer Definition

   Capabilities, categories, rate limits, and authentication are configured and tested.

2. 2. ManagerProwlarr

   Prowlarr stores source settings once and syncs compatible app profiles outward.

3. 3. TVSonarr Search

   Sonarr asks for TV candidates and applies episode monitoring, quality, language, and custom formats.

4. 4. MoviesRadarr Search

   Radarr asks for movie candidates and applies movie profiles, list tags, roots, and scoring.

5. 5. DownloadSABnzbd

   The accepting Arr app sends the selected job to the download client with a category.

Authorized sources onlyA working indexer test is technical connectivity, not permission to acquire copyrighted works.

API key handoffUse internal URLs and keep API keys out of screenshots, examples, logs, and public hostnames.

Sync level	What Prowlarr controls	Operational rule
Disabled	No indexer synchronization to this app	Use only when the app's indexers are intentionally managed elsewhere.
Add and Remove Only	Adds and removes Prowlarr indexers; a down indexer can be disabled in the remote app during sync	Local edits can persist, so document which side owns changes and recheck stale callback URLs manually.
Full Sync	Keeps managed indexer fields synchronized and can overwrite most corresponding edits made directly in Sonarr or Radarr	Change categories, priority, tags, and other Prowlarr-managed fields in Prowlarr, then verify the remote app.

Full Sync does not make Prowlarr the owner of every Sonarr or Radarr setting. It does mean that a local fix to a Prowlarr-managed indexer field can disappear on the next sync. Compare values before and after a controlled sync rather than calling every difference corruption.

Layer 1: Provider to Prowlarr

1. Open the affected indexer in Prowlarr and note whether it is enabled.
2. Run Test once and record the complete error class and UTC time.
3. Open System, Health and History. Find an event at the same time.
4. Temporarily raise the application log level only if the normal log lacks the failing request. Reproduce once, then return to the previous level.
5. Classify the failure before changing the entry: DNS, connection timeout/refusal, TLS validation, authentication, provider limit, or capability/category response.

date -u
cd /opt/media-stack
docker compose ps prowlarr
docker compose logs --since=10m prowlarr

Example expected output shape (not observed): one UTC timestamp, a running container row, and log entries around the single test. Preserve the original error. Before sharing, remove API keys, cookies, session IDs, authorization headers, provider account data, hostnames, IP addresses, queries, and media titles.

A green Test proves that Prowlarr completed its configured test at that moment. It does not prove every query works, the provider has quota headroom, the advertised categories are compatible with an app, or future availability. If the response indicates a rate limit or account restriction, stop testing until the documented window resets or the provider resolves the account state. Do not rotate endpoints, loop requests, bypass a CAPTCHA, or evade an access control.

Layer 2: Prowlarr to Sonarr or Radarr

Test the application entry under Prowlarr Settings, Apps. Use the address reachable from the Prowlarr process, not the address that happens to work in your laptop browser. In one Compose network, that is commonly http://sonarr:8989 or http://radarr:7878. Inside a container, localhost refers to that container itself.

cd /opt/media-stack
docker exec prowlarr getent hosts sonarr radarr
docker exec prowlarr date -u
docker exec sonarr date -u
docker exec radarr date -u

Example expected output (not observed):

172.20.0.4  sonarr
172.20.0.5  radarr
2026-08-24 18:30:00 UTC
2026-08-24 18:30:00 UTC
2026-08-24 18:30:00 UTC

The addresses and timestamps above are illustrative. A deployment will differ. If getent is absent from the image, use Docker network inspection or a temporary diagnostic container attached to the same network instead of installing tools into the production container.

• URL base: If Sonarr, Radarr, or Prowlarr uses a reverse-proxy path prefix, include the required base where the Prowlarr app entry asks for it. A missing Prowlarr callback URL base can produce synced indexers that exist but fail in the remote app.
• DNS: Resolve the service name from Prowlarr's network namespace. Host resolution from a laptop is not equivalent.
• TLS: A private certificate must have a trusted chain and a name matching the URL. Do not disable certificate validation as a permanent repair.
• API key: Copy it from the target app's General/Security settings, never from a screenshot or old note. Rotate both ends if exposure is possible.
• Time: Large clock drift can make logs impossible to correlate and can break time-sensitive authentication. Fix host time synchronization before interpreting a cross-service timeline.

Layer 3: App Sync and Category Drift

Prowlarr synchronizes an indexer according to the capabilities and categories it advertises. The Servarr quick-start documentation also notes that an Arr application accepts an indexer only when its test result contains at least one configured category. A provider test can therefore pass in Prowlarr while an application-specific sync or test still fails.

1. Open the Prowlarr app entry and record its sync profile, sync level, tags, and selected sync categories.
2. Open the indexer and record its tags and currently advertised capabilities/categories.
3. Confirm at least one intended TV category is compatible with Sonarr or one intended movie category is compatible with Radarr.
4. Run the app Test. Save only after the Test succeeds.
5. Trigger one controlled sync, then open the generated indexer in the target app and compare its enable flags, categories, priority, URL, and tags.
6. If Full Sync is active, apply a Prowlarr-managed correction in Prowlarr. Do not keep repairing the generated entry only in the remote app.

Custom provider categories can map into standard Newznab or Torznab categories. Broad catch-all selection may hide a mapping mistake by returning irrelevant results. Start with the smallest category set needed for the app and expand only when an interactive search shows a real coverage gap.

Layer 4: Real Search and Rejection Reasons

Run one interactive search in the affected Sonarr or Radarr instance. This is the decisive branch between "the indexer returned nothing" and "the app rejected what it received." Expand rejected results and read the reason before changing Prowlarr.

Search evidence	Meaning	Next owner
No result in Prowlarr or the app	Query, provider, capability, category, authentication, or limit may be failing	Prowlarr/provider layer
Result in Prowlarr but not the app	App categories, sync state, callback URL, or app-specific query differs	Prowlarr app entry and synced definition
Rejected result with a reason	The indexer worked; an application decision blocked the grab	Sonarr/Radarr profile, custom format, language, size, age, or duplicate rule
Accepted result reaches the download client	Indexer and decision path worked for this one item	Downstream download/import workflow

A rejection such as an unmet custom-format score, wrong language, wrong season pack, size limit, or quality cutoff is not a Prowlarr outage. Repair the owning profile only when the rejection conflicts with your intended policy.

Troubleshooting by Failure Class

Failure class	Confirm	Repair	Validation
Wrong URL base	Compare the configured base path on both ends and the generated Prowlarr callback URL	Correct the owning app entry; with Add and Remove Only, repair stale generated URLs deliberately	App Test plus one interactive search
Container DNS	Resolve Sonarr/Radarr from Prowlarr's network namespace	Attach services to the intended network or use a resolvable internal name	Name resolves after recreate and after host reboot
TLS validation	Identify name, expiry, or trust-chain error	Install the correct certificate/chain or use a trusted internal HTTP path on a protected network	Test succeeds with validation enabled
Credential expiry	Match a 401/403 or documented authentication error without publishing the secret	Issue and store a new key or session through the supported provider/app process	Single test succeeds; old key is revoked
Category/capability mismatch	Compare advertised and app-selected standard categories	Select compatible app categories or correct the provider definition	Expected authorized result appears in the target app
Rate limit	Record response, limit terms, query/grab count, and reset window	Stop retries, lower configured limits to the documented account allowance, wait for reset	One test after the allowed reset; no bypass
Disabled health state	Review System, Health, History, and the first matching error	Fix the cause and let the supported retry/test path re-enable service	Health warning clears and real search works

Rollback and Recovery

If a change creates wider drift, stop. Preserve the new error and restore the recorded value for the one field you changed. For a complete rollback, isolate the restored Prowlarr instance so stale Full Sync settings cannot overwrite production Sonarr or Radarr during startup.

1. Disable the test app entry or disconnect the isolated restore instance from production apps.
2. Stop Prowlarr and preserve the failed app-data directory separately.
3. Restore the pre-change app-data archive and the matching image/package version when a migration requires it.
4. Start Prowlarr privately and confirm the database opens without migration or permission errors.
5. Compare indexers, app entries, sync levels, tags, and categories with the change record.
6. Reconnect one canary app, run its Test, sync one indexer, and run one interactive search.
7. Reconnect normal automation only after the canary passes.

A tar archive is not restore proof. Version compatibility, database integrity, permissions, secret availability, and sync side effects remain unverified until the isolated restore test succeeds.

Validation Checklist

• Prowlarr Test passes once for the authorized canary indexer.
• The Sonarr or Radarr app Test passes using the internal URL and required URL base.
• Container/service DNS still resolves after a restart or host reboot.
• The intended indexer appears in the target app with the documented sync ownership, tags, enable flags, and categories.
• An interactive search returns an expected authorized result or a clear policy rejection.
• Health and history show no unexplained recurring authentication, TLS, DNS, or rate-limit warning.
• The pre-change backup exists on restricted storage and an isolated restore is scheduled or completed.
• Trace logging and enhanced indexer logging are returned to their prior level.
• Any exposed API key, cookie, or session identifier is rotated and removed from published artifacts.

Planned Evidence-Capture Checklist

The following work is required before this article can claim a TechGeeks lab result. Until reviewed artifacts exist, every result remains planned.

• Create artifacts/labs/prowlarr-setup-indexer-management-sonarr-radarr/YYYY-MM-DD/ with an environment record, UTC timestamps, application versions, image digests/package versions, topology, and config hashes.
• Capture a private working baseline and one safe negative test each for URL base, credential, category mapping, and container DNS.
• Pair each Prowlarr Test, app Test, interactive search, health event, history item, and trace excerpt with its command/action and artifact ID.
• Record failure message, affected layer, detection time, rate-limit request count where applicable, repair, recovery time, and post-restart persistence.
• Restore the saved configuration into an isolated instance and prove that sync ownership returns to the recorded state.
• Capture screenshots only with synthetic indexer/app names; record UI version and viewport; fully cover keys, cookies, hostnames, addresses, queries, filenames, and account data; remove metadata; review at original resolution.
• Keep raw screenshots/logs private and publish only reviewed redacted derivatives with captions that state exactly what they prove.

What This Evidence Does Not Prove

• A green Prowlarr Test does not prove Sonarr or Radarr can use the same capabilities or categories.
• One successful app Test does not prove Full Sync preserves an intentional local override.
• One successful search does not prove provider uptime, quota headroom, lawful availability, result accuracy, or long-term reliability.
• A synthetic failure does not reproduce every reverse proxy, DNS resolver, certificate authority, provider policy, or container image.
• A configuration archive does not prove database compatibility or recovery until an isolated restore is completed.

Related TechGeeks Resources

• Build and test the complete Plex and Arr workflow
• Sonarr Homelab Setup Guide
• Radarr Homelab Setup Guide
• Backup and Disaster Recovery for the Plex and Arr Stack
• Monitoring and Health Checks for a Plex and Arr Homelab
• The Complete Plex, Arr, and Tdarr Homelab Media Automation Series

References

• Prowlarr Quick Start Guide
• Prowlarr troubleshooting and logs
• Prowlarr application-data directory
• Prowlarr API documentation
• Prowlarr releases
• Sonarr settings
• Radarr settings
• TRaSH Guides: limiting Prowlarr API use

Final Checkpoint

The repair is complete only when the same authorized canary passes Prowlarr's Test, survives the app connection and sync, appears in a Sonarr or Radarr interactive search with the intended category, and leaves no recurring health warning. Keep the backup and the evidence timeline until the stack has also survived a restart.