How to fix can’t sign into office 365 desktop apps on Windows 10?

Please try the following:

Fully exit out any Office 365 APPs first.

1.  Log off word account and log back in
2.  Remove all the office 365 apps credentials in Windows Credentials

If all failed, please try:

close all office apps

Go to the AAD identity folder in :  C:\Users<Username>\AppData\Local\Packages\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\Settings

Rename Settings.dat to settings.datold

Go to  C:\Users<Username>\AppData\Local\Packages\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\AC\TokenBroker\

Rename folder Accounts to accounts-old