Hi,
SoundTap is a playback recorder, meaning it will record the sound being played on the speakers. On top of that it can also record from the microphone. But to be able to record from microphone, SoundTap should first be recording a playback, audio in speakers. So first try playing an audio and see if it can record that. If so, enable recording from microphone and try playing an audio and recording together with microphone.
Regards,
Yusuf