ATWOOD water heater works on gas, not on electric

Also possible that a terminal in a "quick box" like Trailers and RV's use, has given out from the prolonged high current draw that a water heater represents. With power off, check for continuity of Switch, Thermostat(s) and Element. Disconnect each for testing so you don't see continuity from something else. Then re-connect and power it ON. Do you have 120 VAC at Switch, Thermostat(s) and ONE side of the Element? Other side of the Element is Neutral, should be wired White, and NOT have 120 VAC. If it does, then what happened to me has happened to you. Failed Neutral connection. We have a junction box adjacent to the water heater and that's where the failure was. Easy to fix, but I'd spent a day focusing on elements, switches, thermostats... If you don't have 120 VAC at Switch, Thermostat(s) and (one side of) Element, you could have an open HOT in a splice box. Ours just happened to be Open Neutral.

I am a little late here, but I had the same problem. I obsessed over the thermostat and heating element. After buying both and trouble shooting for days, it turns out it was the SWITCH! I replace the switch and it worked fine for one season. Then it burned out again. Another case of the cheap low quality parts that go into these RVs. Anyway, I finally just removed the switch and permanently connected the circuit. Now I just turn the electric water heater on from the breaker box.

Below is a link to the service manual. Scroll down to the picture of the electric element and ECO on the backside of the heater. First thing to do is see if the ECO tripped, you push it in to reset it. Probably not easy to get to and should have a metal shield over it. Ours worked fine last year but when we arrived in FL this year not working on electric although it worked at several stops on the way down. Reset the ECO and so far it's been ok.

Service manual

You have the 'older' version of water heater--Atwood redesigned their WHs in 2004

GCH10A-3E (Gas Combo Heat exchanger 10 gal 3rd version Electronic ignition)

Your version has separate set of t-stats for each heat source
Your version has direct AC power to electric element---no circuit board control for electric
The element and t-stats are mounted on backside of WH Tank

120V AC power from Circuit Breaker to On/Off switch to the set of t-stats then to element (Black wire 120V Hot, White wire Neutral, Green wire GROUND)

On Edit:
Had to take off this AM before finishing info.

Check the ECO (Hi temp t-stat) ----may need 'reset' (manual button on ECO)
Also should be an OEM On/Off switch locally on the junction box cover over element and set of t-stats

Start at the heating element and check for 110 volts across the terminals. If no voltage, go next to the thermostat and and unplug both terminals and use a jumper wire to bypass the thermostat.

If you have voltage at the heating element but the element does not heat check the ohms to make sure it's not shorted out.

If nothing happens there then take out the circuit board and take it to an RV repair shop and have it tested.

I'm sure I'm leaving out something and others will chime in but it's a start.

Check for AC at the heater then at the coil and this should isolate the problem.