sudden loss of hot water throughout coach both gas and electric. Plugged into 50 amp shore power and initially had hot water after we stopped. Checked both gas and electric switches are on and wTer bypass is in correct position. Doesn’t seem like any power as red light by switches is not lighting up either.  Any ideas?   

Even sillier, but a very easy problem to solve: Check to see whether the sprayer in your utility bay is on. If it sprays, then shut both the hot and cold faucets. When these faucets are open a blind loop of cold water goes through your water heater and after a few moments of hot water, only cold water will come out in your sinks and shower. This has apparently been a problem for Fleetwood rigs years and is known by Fleetwood Service Technicians. 

This fix worked for me; hope it works for you.

I had the same problem with my 2016 Discovery 37R.  Mine was a combination of issues.  First the control board was replaced.  Then, as noted above, I had my valves open on the shower in my sewer/water compartment.  Once I turned off the outside shower valves....poof...the hot water in the coach was fine.