If you are trying to join a Teams meeting and can't get your camera, microphone, or screen sharing working from you laptop you may need to allow MS Teams access to your Camera, Microphone, and Screen Sharing. 

1. Quit Team, then reopen it.
2. Next, open System Preferences by clicking the Apple icon in the top-left corner of your screen and then choosing System Preferences.
3. Next click on Security & Privacy (silver house icon)
4. Click on the Privacy tab and the scroll down to Microphone. Here you want to make sure Microsoft Teams is checked.
5. Repeat step 4, but this time click on Camera.
6. Repeat step 5, but this time click on Screen Recording
7. You may need to restart the Team app again at this point.
8. Quit the MS Teams app and open it again.