Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi Peter Kanake,
Thanks for sharing updates with us and I really appreciate your effort and your precious time doing those tests.
It seems you are able to sign-in via Office 365 online. Since you are getting error message when you try to sign-in into Office 365 application.
Based on my experience and search I will appreciate if you could please try below suggestion and see if it helps for you.
May I know have you tried sign out your account from all Office application and then sign back in again? If not, I suggest you sign out your account from all Office application (File> Account> User Information> Sign out) and then sign back in again to check the results (make sure you use only one account in Office). Meanwhile, please also make sure you are using the latest version of Office suits.
In addition, to check if this issue caused by credentials conflicts, you can also clear credentials to check whether it can solve this issue:
Remove the credentials in the Credentials Manager via clicking Control Panel > User Accounts > Credential Manager > Windows Credentials.
Also, go to your Windows setting> Account> Access work or school>and disconnect all listed account there. See image below for your reference:
If above steps doesn't work for you, then try to Create a new user account under your Windows 10. See if it still alert you with the same error message.
I appreciate your patience and understanding.
Best Regards
Waqas Muhammad