For me it shows the waveform and then "error"

Try disabling CSP for the page

Same here. In Chromium I don't even see the waveform.

I had to turn off ad-block to get it to work.

I can see the waveform but it still doesn't work for me. Switched to Edge, disabled all adblocking and privacy extensions, built-in tracking prevention, and "enhanced site security" (whatever that is), and still no dice. I'd love to try it and be impressed, but it seems impossible. :(

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. :(

I just bit the bullet and did it via python and the api.

Same here on iPhone with Arc Search.