i'm trying to map my djm850 with serato, but my "Midi" button in Serato is greyed out. I've updated the drivers and firmware, but nothing. latest version of serato.

my mixer is mapped to Traktor no problem, so i know it can send and receive MIDI...so i don't know what's going on.

i plug my mixer in, hit MIDI on on the mixer, hit start on the mixer, and even tried changing all of the MIDI channels. but nothing.

help?