This is a recent problem. Can't tell you when it started but today every attempt to download audio from a YouTube site appears to start working but the progress bar remains stopped at 0 bytes of 138mb. Mac Studio - M1
I'm glad I'm not the only person with this issue. my guess is youtube's api changed or something which resulted in the tool breaking. Hopefully it's fixed soon!
We're aware of this issue and are currently working on correcting it as soon as possible. There will be no action required from your end, the video download will resume working as intended in the nearest future.