As the folks above, but if you have. Truma pump in the Aqua roll, then give the connectors a scrub with a nail file or the wife's Nail emery board
.Put the pump into the Aqua roll first before connecting to the van this helps to prime the pump.
Check the water pump fuse, on the main fuse board, a stuck pump as Audio Rob states can burst the fuse.
Borrow a pump from a fellow caravanner, to check it's your pump, but also try your pump on their caravan, this shows your pump is workin or U/S.
If this fails, go to the pub and rethink it all.