A check of the wiring here helps clear a few upfront questions but not a full answer?
This drawing, sheet one seems to match for the load center in your picture!
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/2004/04_f30w_wire_147218.pdf
It seems to show the water heater, if you have option 53D as being on the same 20 amp breaker as the microwave and they only labeled it as micro!
With that in mind, I would first check the microwave is getting power. Light on face on?
That would mean the breaker good but also may put it into the relay shown inline between the micro and the water heater and breaker.
Does it work something like a form of load shedder which cuts off the water heating when microwave is used? Reason for that thought is that a 20 amp would not seem to be enough to power both at the same time??
Any mention in the owners manual of how this might work?
Doing a bit more looking, I find the converter. Are you familiar with where it fits? Looks like under the frig and toward the rear of the load center?
Click these snips to get better view or go direct here:
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/2004/04_f30w_wire_147220.pdf
Looks like the converter plugs into recep. here and then has a strange looking relay mounted on the converter side?
Is this the correct relay as it doesn't seem to give much direct info on it, nor location, but looks at the right spot to serve this purpose, even if not telling us the facts!
If the micro is working and not the water heater on 110AC, perhaps some looking at what happens if the microwave is not being used? I'm guessing the relay should then let the power flow to the water heater but if not, that relay would seem to be a suspect point.
Perhaps failed, maybe just not making good contact, etc, etc.??
Just like Easter? We have to look under lots of bushes to find the right eggs!
