Whale water heater

Hi everyone

Please can anyone help give advice on this problem. Just had our motorhome in for it’s hab check been told the water heater is not working on either gas or electricity. Think they are leaning towards replacing the boiler but not sure, hope not mega bucks l bet!  Rang whale for advice on how to reset it. The guy was helpful and gave us some pointers as to what to try ie fuses out and back in, press reset button but all to no avail. Does anyone have any ideas? Has anyone had this problem?