Hi!
There are two things to check: the audio and the microphone. Have you tested the microphone in another app, such as a meeting app? You can also test it using the Windows Sound Recorder app. Open the Search menu > Search for "Sound Recorder" > Record some audio and see if the microphone is detected.
Also, confirm whether Windows detects a microphone and ensure it isn't disabled under Settings > System > Sound > Input.
Once that's done, we'll have a more accurate diagnosis.