Live tracks present, but no audio?

[occimoron]

I've just started using Jamkazam for band rehearsal during lockdown. I set up my live tracks this morning and all worked fine, but this afternoon they are visible but I have no audio. I've tried deleting and re-installing the Jamkazam app, deleting and resetting up the tracks, but no joy.
I did install a software update before the afternoon session, and also had used GarageBand between the sessions - wondered if these have affected things somehow.
I'm not sure what else to try. 
Any suggestions welcomed.

try re-enabling permission to use Microphone and Camera in your privacy setting.

I was having exact same problem. Using a Mac, went to system preferences, security and privacy, checked microphone access box for JamKazam and that FIXED It! After 2 hours of f***ing around. Thanks jamjam!