Ralph Cramden wrote:
Somtimes Rockwood will install the switch in the knockout for the tank heater if they were not optioned. The switch will still illuminate, but its not connected otherwise. Every Rockwood i've ever been in newer than 2010 or so, including our 2017, has this inside switch for the electric side of the water heater in addition to the one inside the outside access panel of the water heater.

OK...
Dosen't have anything to do with OPs issue
They have been using electric for quite a while and then the electric quit working