If you’ve established that there is a good water supply to the machine then i’d suggest the first thing is to have a good look at the pressure diaphragm and float system on the LHS along with the corrugated hose? If the problem isn’t there then it’s time to start following the wiring.
Run us through the sequence of what actually happens when the machine is started?
the pump comes on at the start and then goes no further have checked water inlet valve ok checked diaphram an is working but can hear a noise from the base like a timer going through a sequence seems to be on the heater manifold?i have never noticed this part or ever had to change this part before .hopefuly this can put a bit more light on this .again many thanks