TL;DR: If your sync stopped working due to an expired or revoked Microsoft connection, you'll need to re-authenticate by connecting your Outlook account again through the app sidebar.
When is re-authentication needed?
Your Microsoft connection may need to be refreshed in these situations:
Token expiry — Microsoft access tokens expire after a period of time. When this happens, the app can no longer read or write to your calendar.
Password change — if you changed your Microsoft 365 / Outlook password, your existing token is invalidated.
Admin revocation — your Microsoft 365 admin may have revoked consent for the app, requiring you to re-authorize.
How to tell if you need to re-authenticate
Your sync was working and suddenly stopped (no events are being created or updated)
You see connection errors in the app sidebar
You recently changed your Microsoft password or your admin made security changes
How to re-authenticate
Open the monday.com board where you have the sync configured.
Click the app icon in the board header to open the Outlook Calendar Integration Plus sidebar.
Click "Connect" to start the Microsoft authentication flow.
Sign in with your Microsoft account and approve the permissions.
Once connected, check your sync configuration — make sure your field mapping, sync scope, and conditional triggering settings are still in place.
If your sync configuration is missing
In some cases, re-authenticating may reset your sync configuration. If that happens:
You'll need to set up a new sync from scratch — choose your sync scope, configure field mapping, and set incoming/outgoing data preferences.
Your existing Integration Column and event links will still be on the board. If the column names and mapping match your previous setup, previously synced events will continue to update normally.
Re-authenticating does not delete your existing events in Outlook or your Integration Column data on the board.
If your Microsoft 365 admin revoked consent, they may need to re-approve the app before you can re-authenticate. See Understanding permissions for details on the Microsoft 365 admin flow.
If you changed your password and have multiple boards with syncs, you'll need to re-authenticate on each board individually.