Korg NanoKontrol2 with Mainstage

Greetings. I am trying to get a Korg NanoKontrol2 to work with MainStage 3. I am using 3 USB controller keyboards (a CME XKey, a CME XKey37, and an iRig Keys). All three of the keyboards are set up via a powered USB hub and working properly. I am now trying to add a Korg NanoKontrol2 to the set up to control track volumes. The NanoKontrol seems to be recognized by MainStage, as I see the MIDI numbers changing when I move a fader, but it's not controlling the track volume faders. An example: when I play a key on any of the keyboards and move a fader on the NanoKontrol2, it alters pitch rather than volume. I use the NanoKontrol2 in both Logic and Ableton Live, and it maps to the track volume faders just as it should. I just need the NanoKontrol2 to map to the volume faders in MainStage and it just won't do it. Any suggestions would be greatly appreciated.

Specs: 2011 MacBook Pro/OS 10.11.4 - all versions of the software mentioned above are the latest upgrades.

Thanks very much.

Ron