You need to install the software that comes with it (or from Focusrite's website) it's called something like MixControl - and you need to choose 'DAW 1, 2, 3, 4' for each of the outputs. That may not make much sense but have a try and I'll post some screen shots later if you still can't do it.
Basically MixControl is setup for sending inputs to outputs rather than audio from QLab/ProTools/anything else - so you need to make that change before getting QLab to play ball.
Let me know how you get on.