Behringer XR16 and Behringer P2 Panning Guitar L or R

Have a Behringer X16
Guitar plugged into channel one
Aux 1 goes to a Behringer P2 headphone amp and headphones

Using the X Air software, is it possible to pan the guitar in the headphones so that the guitar only comes over to one side of the mix.
Tried all the panning options in the software which doesn't seem to have any affect. Tried changing the P2 from Stereo to Mono with no affect.

New to all this. Is a stereo guitar signal required to pan?