Assigning channel strips to my midi device

hi

i am using MainStage 3 and using the mpx8 for triggering sample/loops etc...

MainStage seems to recognise the mpx8 ok and the pads on the device can be assigned to the onscreen software pads on mainstage with out any issues but on the channel strip settings in MainStage under the 'midi input' tab, the mpx8 does not show up.....

this means i can't seem to be able to actually trigger any of the samples on the channel strips.

does anybody know why this is?

thanks