Here is a list of things that you should check if your microphone is not working in a Teams meeting:

1. Check that your microphone is not muted
2. Adjust the microphone gain level
3. Ensure that your headphone audio levels are not too loud
4. Check that the correct microphone is selected as the default recording device
5. Close any applications that may be using the microphone
6. Check that your speaker and microphone are not muted in the teams app
7. Run the audio troubleshooter