Hi - I've fitted an aftermarket cc kit to my 2000 Passat 1.8 Sport (vw parts) and I can't get it to work ???

I have an EPC light and accellerator black box.
I have checked and double and triple checked the wiring.
I have activated the ECU with VAG-COM and the vehicle code displays a "G" in amongst the other numbers.
When the CC switch is in the "on" position and I start the car, I get a brief flash of the green CC light on the rev counter.

The CC doesn't work while stationary in neutral or while driving.....

Anyone got any ideas?

Cheers in advance