Teams on macOS only shows a blank white screen

I just had this happen with the New Teams (work or school).  Initially upon installing the new version, it worked fine, then there was an update - and after that Teams would only launch with a blank window (slightly transparent, only the 3 buttons in the top left).  Logs didn't seem to have any clues as to exactly what was failing.

In my case, the old version still worked fine - but nothing seemed to get the new one to display anything. Signing out of the old one didn't help. Tried many things over a couple of days.

Finally doing a search I found another Teams folder in

<user home folder>/Library/Containers/"Microsoft Teams (work or school)"/Data/Library/Application Support/ then "MSTeams" folder - dragging that one to my desktop, then starting up teams again has restored the New Teams to a functioning state.