I have this same problem on a laptop (HP Envy x360 Convertible 15m-ed0xxx) with Windows 11 Home and Realtek drivers, and the Win11/Realtek combo seems to be the culprit as noted by others. As suggested in another thread back in January 2022 about this same problem, I connected to a Bluetooth sound device and made sure my audio source was playing through it. This apparently makes the PC bypass the Realtek drivers, as the SoundTap software was then able to detect the audio stream and record it while the audio played over Bluetooth.
It's a weird workaround, but it worked for me and the SoundTap recordings were of good quality. The original thread is here - scroll down to January 19 through January 21, 2022 where this workaround is discussed. https://nch.invisionzone.com/topic/37782-soundtap-is-recording-nothing-dormant-waiting-for-audio/
