I created a new project
Then went back to the other project I’m working on
And the mixer looks like this, and track 2 can be heard playing from step 3
All else is silent… And track 2 plays on even when I mute it… What have I done?
Any help is welcome… 
Looks like you hit “solo” for track 2. You do this, I guess, with “cue” (?) and track-button in mixer mode. Better check the manual to be shure what the button-combo is …
Cue+ trigkey inside mixer screen
Thank you !