Trouble setting up electrics on b44.1 buggy

[Ashlandchris]

Hope someone can help - I have purchased a 2nd hand b44.1 which I am currently putting electrics into. This is my first one for 25 years so a bit baffled by all new ESC and brushless motor stuff.
I have got all installed and steering servo works, but motor only runs in reverse (i.e. When throttle trigger pushed away, not pulled).

I am using an Absima crp3 radio with speed passion reventon S with v3 9.5 motor. I think everything is set right so is this simply a programming issue for the radio?

Any advice gladly received