Truma ultrastore water heater not working

Morning all. We have a 2011 Nuevo II ES with Truma ultrastore water heater. On a recent outing I noticed that the water heater doesn’t work on 240v. It works ok on gas. Has anyone successfully managed to diagnose this fault? Any help much appreciated as I can’t work out how to access the 240v connection to the heater to test it! Many thanks

Just a thought for you. I have the Combi 4e and if either the 12V or the 240V is interrupted while the heater is on (deliberately or by accident) then the unit will not function until the control knob is switched off and on again. It's a safety feature. Not sure if the Ultrastore has the same safeguard.