On most atwoods there are just two T-Stats. Operating and emergency cut out so if it works on Gas, those are good.
Now on the backside (inside) you will find a black box with wires running to it, Two of those (Black/red) are 12 volt.. Put a test light on them and see if the light lights. Hear if the relay clicks.  Now you have 120 volt wires.
Make sure you have 120 volts coming in and out to the element,  If so replace element. if not,< Well you now know what's not working.