Trace and test the wall socket it is connected to. Unplug the dishwasher and plug in your hairdrier. It’s the easiest and quickest way to check a functioning socket. If there is no power at the socket, look for a remote switched spur above the work surface. Try all of them, still checking with your hairdrier.
If there is power at the socket (hairdrier runs) then there is an internal fault and the machine should be checked by an engineer.
Diplomat is MFI’s pet name, so if it’s under guarantee, call them. If not, click the Repairs @ banner on this page to contact a UKW approved engineer in your area.