I used an APC20 with QS, I used Bomes midi translator, I remember I had same issue. Later found that the midi channels in QS where only looking at Bomes midi translator, as the slider also need to be configured through Bomes so that QS will pick up the signal.
Please dont ask how I did it as it was some time ago, and I'm not good at that sort of thing. It took ages to work out, but when I found the problem it all worked well. The only reason I never stayed with the APC was that QS offer no feedback to the buttons, so you never really knew what had been pressed.
Tony