No Playback in Pro-Tools Free

Hey all... first post and brand new to Pro-tools (and recording, in general), so I'll try and be precise. I have a 2012 Mac Pro and my I/O is an Apogee Quartet. I have been use Logic X, but I have some PT sessions that need to be consolidated before another engineer can mix in Logic. I downloaded PT Free and the sessions pull up, but I have no sound on playback. I've defaulted the routing and my quartet's headphone meters are moving, but no sound. Please help!