on board microphone not working

Hi Ro8orob,

Thanks for coming to Apple Support Communities for help today with your mic on your MacBook Pro. It sounds like your external mic works but not the internal mic.

Have you tried resetting the NVRAM? Reset NVRAM or PRAM on your Mac

You can also try testing inside a new user to see if the issue is isolated to your user or system-wide. Here's How to test an issue in another user account on your Mac. If you find the issue present inside the new test user account, the likelihood of this being a hardware issue increases.

Let me know how it goes.

Have a fantastic day!