Didn't you post a similar thread just a few days ago? What about my suggestion on testing the sound in OBS for the capture card?

Not only did they post this same issue last week, they said they figured out their issue and got it all fixed. Also, you have a run from 4/21/2020 of a game played on an NES and it has the game audio in it perfectly fine.

Did you fix your issue then have it stop working again? What did you change in your OBS settings over the last two days since you had the audio working?