If you see an error such as:
Possible xero-tenant-id header issue. Xero Error: AuthenticationUnsuccessful
this means the connection between MechanicDesk and your Xero account has expired or become invalid.
How to Fix
You can fix this directly from your MechanicDesk account:
Go to Settings → Integrations
Click Unauthorise
Click Sync > Quick Sync
This will prompt you to log back into Xero and reconnect MechanicDesk to your Xero organisation
If the Error Persists
Check that you’re logged in with the correct Xero account
Confirm MechanicDesk is listed under Xero → Settings → Connected Apps
If you’re still seeing the same message, contact MechanicDesk Support and include your workshop ID plus a screenshot of the sync log