I’m using a Super USB Cassette Capture on Mac 10.15 Catalina. My microphone setting is enabled and I can hear the tape playing but I only get a flat blue line and no sound is recorded. I didn’t see any explanation except about the microphone setting in the manual. Any ideas?
Go to Apple (menu) > System Preferences > Sound > Input. In the list select the one that contains “PnP”. Play a cassette. Does the input level meter bounce? Stop and start the cassette. Does the input level meter still bounce?
If it passes this test, start Audacity, select the “PnP USB Audio Device” (or whatever it is called) and see if you can record.
Lots of Mac users have trouble with these cassette-to-USB devices (that are sold under various names but appear to be all the same). I don’t know of anyone who has managed to get one to work reliably.