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Open the source and read the message under its status badge. Every failure shows a plain-language reason and the fix. Sync failed means the sync stopped early. Partial sync means it finished but couldn’t sync some documents. In both cases, everything that did sync is already searchable. The most common reasons:
  1. The source rejected the saved credentials. The account that set up the source lost access or its connection expired. Reconnect the source, then run Re-sync from the source’s menu.
  2. The system was temporarily under heavy load. Nothing is wrong with the source. Run the sync again. If it was a scheduled sync, it retries automatically on the next run.
  3. Some documents didn’t sync. The source page lists each affected document with the reason. Temporary issues retry automatically on the next sync. Documents the provider refuses to share (unsupported formats, revoked access) stay skipped until that changes.
  4. Brain couldn’t read group membership. This applies to sources with Document access set to Original source. Files shared through groups may stay hidden from search until an organization admin checks the organization’s directory connection, or someone reconnects the source with an account that can view users and groups.
  5. Someone paused the source mid-sync. Not an error. Resume the source and sync again.
If a source’s last 3 syncs in a row fail on the source’s side, Brain pauses the source and emails the person who added it. Source-side failures are a rejected connection, no credits left for Company Brain, or an unreadable part of the source. See Automatic pause after repeated failures. Whoever ran the sync also gets a failure email with the same reason, so you don’t have to watch the page.

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FAQ

Sync failed means the run stopped before finishing. Partial sync means the run completed, but specific documents were skipped — open the source to see which ones and why.
Documents skipped for temporary reasons are retried on the next sync automatically. Documents skipped because the provider would not hand them over stay skipped until the underlying cause is fixed.
It is hidden from search, not deleted. If the source shares it again on a later sync, Brain re-indexes it with fresh content and permissions. If access is still denied after 30 days, the hidden copy is removed. See Why is a document missing?
No. A failed sync never removes what was already indexed — search keeps working with the content from the last successful sync.
Reconnect the source’s credentials and check its settings. If it still fails, contact support.

How often does Brain sync?

Automatic and manual syncs

Why is a document missing?

Permission-based reasons