With the newer versions of MacOS, users need to grant permission for applications to use “Screen Recording” if you want to share your screen via Teams, BigBlueButton, Zoom or a whole bunch of other apps. When you first go to use the feature, you should be prompted to give permission:
Many users accidentally “Deny” this prompt and then are unable to use advanced features. To enable it afterward, you need to open System Preferences and go to Security & Privacy. This will allow you to enable “Screen Recording” for that app.
Beware though: once you enable this, the app will need to close and restart so it is best to do it ahead of time!