No audio from mac (logic or anything else) is coming through my ZEDR16 mixing desk???

Hi guys.

This is something that has been really annoying me. I can't get any sound from my mac back through my ZEDR16 desk. It's communicating with the computer (through firewire connection), and I can record into logic and everything, but no sound comes back through the mixer from logic or anything else. I can't hear a thing??

In Audio midi setup, it is selected as the default input, default output and system output however all the volumes are down at zero, highlighted light blue, and won't move. It is also set to ZEDR in the logic audio preferences. This has been fine for other desks i've had, and sound has come through fine on those.

I would really appreciate any help

Well I only got the desk today and every other aspect of it works. I'm not sure if it's just my computer playing up or what. Everything else is fine, its just not getting any sound from the mac playing back through the mixer.