Did you check if your mic even works in principle? E.g. using https://www.onlinemictest.com/
If you don't get sound there it won't work anywhere. A surprising number of problems like these can be solved by selecting the correct audio input source (provided your computer shows more than one).
Yep. Mic works fine. My mic even works on the test page! What doesn't work is any of the transcription functionality. :(