ATWOOD water heater works on gas, not on electric

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.