If your audio is not working, restart your computer. If it's still not working then check which microphone your browser is trying to use. On Chrome it is on the right of the URL bar and a little camera icon, on Firefox it is on the left of the URL bar.
If it only gives you the option of "VDP Source", you'll need to disable that device before you can select your built in microphone.
If you are still having trouble, please email us at firstname.lastname@example.org