I found a solution to an annoying problem:
After updating to the new Microsoft Teams, I could see my camera in the preview screen, but when I was in a meeting, I’d only see a black rectangle as myself. Other people mentioned that they could see me, though sometimes my video would drop off. Also, I was unable to see anybody else’s camera feed, nor could I see when people shared their screens.
Read on for the cause and solution that worked for me.