If you're using LiveProfessor on macOS and experience no audio input despite correct audio connections, it's likely due to macOS security policies.

When starting LiveProfessor you have to click “Yes” when macOS asks if it is OK to use the microphone.
By "Microphone", Apple means any sound input.

You can verify the setting in macOS under Settings > Security Settings > Microphone. You should see LiveProfessor in this list. If it is not already present, you should be able to include it there.