Posting this in case anyone else runs into the problem…
 
I recently tried to use Rapture Session with a guitar patch to see if I liked the sound better than the celesta that I currently had. When I tried playing the newly created track there was no sound. Nothing. I close and reopened the project and there was sound if I clicked on the mini keyboard in the Rapture app but as soon as I tried to play the track, sound stopped and the mini keyboard was useless. It turns out this was a song that was exported from Logic and imported into Cakewalk by Bandlab and it contained some midi instructions at the beginning of the event list that were messing up Rapture Session. I removed those events leaving just the note events and everything finally worked as expected.