I am also having trouble getting this to work properly... However, I am having the opposite trouble, where the gate is working as expected, but I am not getting any pitch control. The wiring of the cable is odd, I am using an Apple AV cable (TRRS-3xRCA) which may be part of the problem, I'd suggest you try a different cable. At one point I swear I was getting pitch, but it was inverted--now nothing though which make me suspect the cable.
In the meantime, with the Minibrute gate out to sync in on the Monotribe(while the MT is in sync mode, not CV mode), MB gate switch set to KBD, will get you tempo sync with the MB arpeggiator, giving a type of midi sync for the monotribe (I know there is midi mod, but this works stock), which is proving quite useful and fun.
Also interested to hear if anyone has gotten both pitch and gate working with the Minibrute/Monotribe setup. thanks