Office 365 backup fails.
MESSAGE Cannot back up the primary mailbox of an Office 365 user: 'folder: mailbox primary root: token validation failed'
Cannot back up the primary mailbox of an Office 365 user: '[ews-code=ErrorNonExistentMailbox]: The SMTP address has no mailbox associated with it.'
Error 1: required permissions have been revoked from Acronis Agent in Office 365.
Error 2: the software detects that user has been deleted during discovery activity, which is scheduled once per day. After this deleted user is marked as "grey" and no more backups are executed by schedule for this user. "Grey" user will be deleted from the Backup Console after 7 days in that state.
Solution for error 1
Re-register Office 365 account:
- In the Backup Console, navigate to Devices -> All devices.
- Click Add.
- Select Microsoft Office 365 for Business.
- Confirm granting permissions when prompted.
Solution for error 2
You can force discovery of Office 365 organization by clicking Refresh on Office 365 organization group.