Is it a single cab tipper?
I have a crewcab tipper with an 8ft tipping body, my mates single cab has a 10ft tipping body, but the ram is the same distance from the back of the truck, which means his has to lift an extra 2ft of body at the front.
If he has any weight at the front it wont tip it up, and you have to give it a lift at the front to help it.
He solved the problem by making some spacer plates, I think they are 2 inch box section, and welded them on the front tipper body chassis pads where the tipping body sits, so that it wasnt so low to start off with, as the Mk5s always lean forward, and this seems to help his out.
The ram leaked slightly on mine when I bought it, but it has sorted itself out with use, I dont think it was used much for abit before I bought it and the seals had dried out.
If on the other hand your ram is loosing pressure by leaking badly, and it wont lift with any weight on, then you may need the ram servicing.
Might be a completely useless tired rambling, but might help!