Teams Desktop App Not Loading (Crash Loop)

Solved.

I was able to interrupt the crash loop. As the loading screen was showing (for a few seconds at most) it would also pop up the icon in the system tray. I waited for the system tray icon to load, then quickly right-clicked and hit 'Sign Out' from the menu. This took a few tries as it sometimes crashed before I could hit the button.

When I did finally hit the Sign Out button, it popped open the sign-in window and I was able to see the problem.

The username that was pre-filled in the sign-in window was username@local.domain instead of username@email.com. Since the username@local wasn't working, it seemed to be causing the crash. When I changed it to the correct email address, it all worked just fine.

A strange error - and odd that this would be the behaviour of the program when a pre-filled login did not work. Also weird was that it only happened to two users who had previously been using Teams, whereas new users with no prior Teams install were unaffected.