djcontrol inpulse 300 with traktor pro 3 / headphones problem

hi

thanks in advance for your help

i connected the djcontrol inpulse 300 to traktor pro 3, downloaded a map file and have a problem.

when i plug in a headset i can only hear the master channel, when i turn off the master button i cant hear anything (which is normal) but when i press the headphone button on one of the channels i cant hear the music

something having such a problem?