I've had a chat with one of the other forum helpers about this issue, and neither of us can figure out exactly what the problem is.
The fact you were able to record the cassette player plugged into the interface shows that the computer, Audacity, the interface and the interface drivers are all working correctly.
The problem is somewhere between the mic and the interface, but as we can't get our hands on the equipment we are not able to trace the problem any closer than that.
Cannot Get Audacity 2.4.2 to record. Tried everything--even two different computers.
Forum rules
This forum is for Audacity on Windows.
Please state which version of Windows you are using,
and the exact three-section version number of Audacity from "Help menu > About Audacity".
Audacity 1.2.x and 1.3.x are obsolete and no longer supported. If you still have those versions, please upgrade at https://www.audacityteam.org/download/.
The old forums for those versions are now closed, but you can still read the archives of the 1.2.x and 1.3.x forums.
This forum is for Audacity on Windows.Please state which version of Windows you are using,
and the exact three-section version number of Audacity from "Help menu > About Audacity".
Audacity 1.2.x and 1.3.x are obsolete and no longer supported. If you still have those versions, please upgrade at https://www.audacityteam.org/download/.
The old forums for those versions are now closed, but you can still read the archives of the 1.2.x and 1.3.x forums.
Re: Cannot Get Audacity 2.4.2 to record. Tried everything--even two different computers.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)