in the Keys. Have a Girard tankless. Set up as usual and later the wife complained there was no hot water. Hmm. Looks like no flame. Reset/on/off/pulled fuse, nothing. Was bumming. Then someone on You Tube mentioned this. Well it turned out the RV park water flow was below the threshold for the heater. Wouldn't light. I switched over to the tank & coach pump and works just fine.
Knowledge gained. You Tube is the balls.