garageband 2021

I recorded 4 tracks on garageband , two were midi tracks that I played on my keyboard.

Everything played fine --sounded very good. But now when I try to play the tracks, the one midi track

( which was a bass line ) does not play at all! I can see the recorded music but nothing . When I turn up the volume on the track, it starts to feedback! I have never encountered this before. I tried copying and pasting this track to a new one but there was no sound...

Help! JanS