Track mysteriously don't play sound?

I made a song, and my drum track and bass line track don't play sounds in one sequence. Other sequences are fine. I did not mute them or apply automation to them. It happened seemingly randomly. They played sounds and now they dont. I can't get the tracks to have sound despite deleting the notes and pasting them back, etc. . Actually the pads don't register sound when on the sequence and track indicated and pressed. I am in version 3? Any thoughts on this - bug or did I do something to mute the 2 tracks in this particular sequence inadvertently and in unison across those tracks.

I'm not sure if it's directly related to your issue but on MPC3 I often experience situations especially with plugin tracks where sound randomly stops playing. In such cases tweaking a parameter on the plugin usually gets the sound working again.