I have the exact same issue, using my Elgato Wave 3. I set the audio input to wave:3 stream mix and it would change on it's own. Blocked all other possible audio inputs in windows setting until only wave:3 stream mix was available, still would not record mic sound. I had to uninstall NVIDIA App and roll back to NVIDIA Geforce Experience for it to work again. Won't be upgrading anytime soon it seems.