No reverse with new controller

[haggis]

Hi, ive got a Team associated b4,1 rtr.

Ive installed my hitec aggressor radio with the atom receiver and although it works great forward and brakes well i cant seem to get reverse

ive tried adusting the trim, the throttle exp and resetting the settings but i cant get reverse

i'm that bad of a driver that ill need it a lot so any input would be great!