Office 365 backup fails with:
MESSAGE Cannot back up the primary mailbox of an Office 365 user: 'folder: mailbox primary root: token validation failed'
Required permissions have been revoked from Acronis Agent in Office 365.
Re-register Office 365 account:
- In the backup management console, navigate to Devices -> All devices.
- Click Add.
- Select Microsoft Office 365 for Business.
- Confirm granting permissions when prompted.