I just updated to Catalina yesterday. (Ignoring the fact that it took a long time AND hung on the “setting up” step.) This morning I opened up Microsoft Teams, hopped on a meeting, went to share my screen and got a pop up. In general (and this morning), my instinct is to dismiss a pop up until I can actually read it later.
However, this meant that I now could not share my screen on my Teams meeting. My only option for sharing was my screen background. Not very useful. Once I ended the meeting, I couldn’t find or remember what the pop up said.
It’s a new setting, where you have to allow “screen recording” to Teams.
Go to your mac’s Settings. Then Security & Privacy. Then Screen Recording. Select Teams and you’re good to go.