For some reason in O365 when we share a document in OneDrive for Business and the sharee chooses to 'Open in Word' , it will launch Word and prompt for their O365 login. Not normal as it only happens for some users.
The fix we have found is to clear all the O365 credentials in the Credential Manager and then add the account and OD4B service back in Word. Then when we choose Open in Word it works fine and we can open the document without this additional login prompt.
Our affected users are frustrated with all the additional log-in prompts so we are wondering what might be causing this - perhaps the recent upgrade to windows 10 or the upgrade installation of Office 2016 itself. We are not sure if it will happen again somehow and then we have to keep clearing the credential manager. Also having to hit each machine to do this is not a good...