I've been experiencing the same issue with Microsoft . Teams is forcing me to complete three stages of security, the authenticator (which I thought was enough ), text, and password. When I complete all three I am then told that my phone number is in use with another account...but it cant be unless someone else as mistyped. I now cant log-in to Teams and find Microsoft support pages at now more than fisher price level.
Second issue I have with Teams is that I receive a black screen despite camera being in use. The camera works on all other apps such as Teams. I'm hoping by signing in that the Teams app may display the camera...I'm not holding out much luck. Microsoft are such a huge organisation but some of their recent software feels like it has been developed in a spare bedroom for a college project.