HI Mate

If this is the same type of truck I have worked on a few months ago, one uses the Zapi controller the other uses the BOSCH LT200 Controller. Either way if a fault as such has occurred it should throw up the error on the dash. Whats coming up on the dash when you start it up and when you try drive? It may be that your missing an interlock like seat handbrake etc?

I think with the Zapi unit there is a connection on the dash which flashes a Red LED indicating an error