Help please - Fault with Candy Dishwasher - DFI85S?

I have a Candy dishwasher model DFI 85S. Last night, during the wash programme, water was escaping from the underside of the door. I thought the filter might be blocked so I cleaned it and re-set the programme. Very shortly after the prog. re-started, the machine emitted a muffled bang noise (a bit like an electrical fault?) and stopped.
I manually emptied the water from the machine and cleaned out all the debris and filters. I re-set the programme but nothing has happened (but the indicator lights were working). Having referred to the manual, I note that the machine is fitted with a “water-stop” device. The “window” of the device appears to be red? I’ve un-done the value but can’t work out how to re-set the device. Do you think that this is the cause of the problem or could it be something else or both?
Many thanks for any assistance you can give
Peter