I am also having the same issue, but after removing the below registry and folders, the issue has been resolved, but for some time it has not worked.
Note: Take the backup and check the below steps.
- Log out of office 365 accounts in word
del C:\Users%username%\AppData\Local\microsoft\office*.* /s /q
del C:\Users%username%\AppData\Roaming\microsoft\office*.* /s /q
reg delete HKEY_CURRENT_USER\Software\Microsoft\Office /f
- Logoff / login again