No audio in VRC if the default input/output audio devices have unequal sample rates.
How to replicate the issue:
  • Close VRC
  • Go to Windows' Sound Control Panel
  • In the properties of the default Playback/Recording devices under Advanced tab make sure that their Default Format frequency is set 44100 Hz on the Playback device and 48000 Hz on the Recording device, or vice versa.
  • Now run VRC and you'll not hear any sound and there will be no devices to choose from in the VRC microphone settings. And if you watch other ppl talk, you will not only not be able to hear them but their nameplates won't light up as if they're not speaking at all.
Audio in VRC will only work in this case if the default Playback/Recording are set to the same sample rate. For example, if both of the devices are set to 44100 Hz or 48000 Hz or whatever, just as long as both are the same.