I am helping someone in our Office 365 tenant with a strange sign-in problem that affects only his Windows profile, and the issue is NOT in the Credential Manager.
This is his home computer running Windows 10 Home, build 1703. He is running the latest Office 2016 (installed the click to run apps from Office 365)
The problem began after he changed his Office 365 password. He can sign-in to the Web apps on another computer, and he can sign into Office 2016 apps on the same computer using a different Windows profile. For the problematic profile he signs into Windows using his personal Microsoft account. Then he signs into Outlook and Office 2016 with his Office 365 for Business account. Shouldn't be a problem...I do the same thing at home. The issue is that Outlook, Word, Excel, etc. will prompt him to sign in. When he enters his Office 365 email address (UPN), the sign-in screen immediately disappears without prompting him for a password. The sign in fails and Outlook says "Disconnected... need password)."
The first thing I checked was Credential Manager, because that is usually the issue for things like this. We removed everything Microsoft or Office related from credential manager. It didn't help. Then we removed everything from credential manager, and it still didn't help. Repairing and then reinstalling office did not help.
I know that the problem is in his Windows profile, because he can sign-in just fine on the secondary Windows profile we created. So my question is this:
What do I need to delete from the registry and/or from the C:\users\username\appdata folder to resolve this issue with his Windows profile?