Hi Nylas community,
We’ve been experiencing a recurring issue for about a month now where one of our users gets a 404 “No Grant found for this Grant ID” error when attempting to send emails via the Nylas API.
What makes this confusing:
- The Grant ID we have stored in our system matches exactly what we see in the Nylas dashboard — the grant exists and appears valid.
- We deleted and recreated the grant for this user, which temporarily resolved the issue — but the error came back recently.
- Our error logs consistently show the same Grant ID being used in the failing requests, so it’s not a stale/mismatched ID on our end.
- This issue only affects this one specific user — all other users are sending emails without this problem.
What we’ve ruled out:
- Mismatch between stored Grant ID and actual Nylas Grant ID (verified manually)
- Typos or encoding issues in the Grant ID
Questions:
- Could this be related to the user’s mailbox itself? The fact that the issue only affects this specific user and keeps coming back even after recreating the grant makes us wonder if the problem originates from their email provider (e.g., revoked OAuth permissions, account restrictions, security policies, …).
- Can a grant appear valid in the dashboard but be in a broken/invalid state internally?
- Is there a way to programmatically verify grant health beyond checking its existence?
- Could there be a race condition or replication lag on Nylas’s side that causes grants to intermittently appear “not found”.
- Are there known cases where a grant needs to be re-authenticated even if it still shows up in the dashboard?
Any insight would be greatly appreciated. Happy to share more details if needed.
Thanks!