Firefox 75.0 (64-bit) on Windows 7 with Tracking Protection and uBlock on. Doesn't work with both turned off either.
Error occurs when microphone is not plugged in and when I deny microphone permission in browser. Probably a very rare case, but my microphone connection is a bit wonky and sometimes I have to re-plug it to work. It would be awesome if your app showed that I might have a problem on my end.
I see cool, ill look into some better error handling!