This happens to me all the time. In my case they are actually muted even though the muted button is not activated. The fix for me has been to click the MASTER Mute button at the top left side of your project window. It’s a major pain because then it obviously unmutes EVERYTHING and I have to go back and remute the tracks I may have had muted for a reason.
Well my problems sounds a little different for yours in that I don’t see any movement on the meters. Mine is obviously a bug which means Steinberg will get around to fixing it. They usually are very responsive in tracking down and correcting the problem, at least that has been my experience.
Next time it does it try the “master mute” button and see if they come back to life. I’d be curious if it corrects your problem since you are on Win7. I’m on a Macbook. I was going to wait to see if others had this issue and post a bug report so we can track it down and get it corrected.
Sometimes happens to me when I import a MIDI file.
One or more tracks just will not ‘sound’.
(this does not happen to me using audio tracks)
Rather than taking time to figure it, my work-a-round is to:
1-Find a track that will sound.
2-Duplicate it.
3-Remove all MIDI info from the dup.
4-Copy the MIDI info from the track that will not sound
5-Paste that info into the dup track that does sound.
6-Remap the sound source/patch etc.
7-Delete the old non-sounding track and bob’s yer uncle’.
From then on whenever I open that project, all is well.