Hi Dburne can you give the indication of the mic you bought? thanks.
😐 I bought a $120 ModMic Wireless to solve the Rift S microphone problem last week.
Now I saw this thread
For about a couple of months I had no problems with Rift S but one day suddenly, while using voice commands in X-Plane, the mic stopped working. Replugging cables, USB and Display Port did not help. Restarting did not help. I disconnected the PC from the mains for a few minutes and the problem seemed to be resolved but only for about half an hour. Changing USB port also helped for a few minutes. Then I tried disconnecting other mic devices from my PC and left the USB cable in the newly chosen port. I think this has solved the problem as everything is normal since I made those changes about a couple of hours back. I hope it helps others and myself as well forever.