Wayne
First thing, have you checked the flow switch inside of the waste tank? if its in the "up" position it'll cut out the vacs. Unscrew the plastic tube an cleaned the switch. Make sure its straight, not pointing up.
Second
Open up the machine. Look for a couple of black wires that go from the motor or power supply (cant remember which), up into the top half of the machine. These two black cables should be going in to a small white, wire connector (the one that you screw the wires into). One or both of these wires might have disconnected. Two going in, two going out.
The wire connector in question is located directly above the pumphead. Part of the cluster of wires and hose that goes up in to the body of the machine (where the switches and regulator are found).
That'll be £10 please