I'm having a similar issue.
All of a sudden my video no longer works and is actually showing a blank white screen instead.
I've restarted the comp, checked privacy settings, checked for webcam driver updates (there were none) and reinstalled Zoom, with no changes.
My video works on all other apps, so this makes me think it's a Zoom bug against certain webcam drivers?
There were moments when I first noticed the white screen, where it would flicker back to the video for a couple of seconds then back to the white screen. That has not happened for a few days now and remains white.
I've even tested of different Zoom accounts.