Atwood 6 gallon Water Heater - Not working on Electric..

It seems you have a wiring/connector/switch issue. I'd suggest to clean up all the connections as a start.

Anytime I'm worried about a fuse/pin/spade connection being oxidized or dirty, I break out a spray can of Caig Deoxit. A drop or two and working the connection renews the metal surfaces. Deoxit is available at Guitar Center and some Radio Shack outlets. It's also sold online. I haven't found a deoxidizing cleaner that works as well as Deoxit. Typical electronics cleaners don't work nearly as well.