Some mailboxes in the archive groups are not being archived (4311877)

One or more mailboxes in one of the archive groups is not being archived

1. Open Enterprise Manager, click Tools > Address Book Manager.
2. On the Mailboxes tab, right-click in the window on the right, then select Add/Remove columns.
3. Add the Activated column and click OK. Doing this will allow you to see which mailboxes are activated or deactivated.

   

4. Right-click on the affected mailbox and select Activate mailbox.

   

Note: For Online Exchange it's expected behavior blank folder like Inbox if user is blocked in office 365 unlike on-premise Exchange.