Just a shot in the dark....
It seems as though your cruse is being told to disengage.
Does your light bar have running lights/brake lights.
If so it might be that a running light is cross wired to a brake light and electrically telling the cruse to disengage (or in this case NOT to engage) sort of like you hitting the brake.
Try disconnecting the light bar, and the tail lights on the trike kit and see if it works then.
2 cents