OneDrive for Business – ​The server you are trying to access is using an authentication protocol not supported by this version of Office.

We ran into this error and found the following fix at

1.Accessed Control Panel > Selected the Microsoft Office Subscription > right clicked > change > Selected Online Repair
2.Removed all the stored credentials in the credentials manager (control panel > credentials manager)
3. Restarted the computer
4. Deleted the folder’s below:
5. Sign in Word (opened blank document > file > account > signed out and signed in office 365 account)
6. Started OneDrive for Business. ( from the search bar typed OneDrive for Business> clicked on the app > sync a different library instead >pasted the url of the team site “Public documents” > sync now​