Issue: I closed a pop-up window when I was getting into Microsoft Office and now I can't do anything with Office.
Environment: Anywhere people may use multi-factor authentication when logging into Microsoft products, including computer labs
Resolution: It could have been that the pop-up message window that you closed was asking you to authenticate using Duo. The only way to access Microsoft apps is to re-launch the app and use Duo to log (authenticate) into it.