This is probably old hat but...
If you actually ran the LP lines dry, sometimes it takes longer to purge the air from the lines for one appliance than the others (although I'd think that the water heater was the first in line... but it depends on the layout of the coach...). To aid in purging the lines of air, I generally light each of the stove burners one at a time until they're all going, then shut them off. That generally moves enough LP through the lines to get it close enough to the other appliances that they light pretty quickly. I figured that out with the old manual light fridge in the Safari after waiting FOREVER for the air to purge at the fridge.
I'd agree that it'd be worthwhile to check and clean all of the electric connectors. I'd probably also blow out the "chimney" in the water heater with compressed air just to make sure that you don't have any spider webs or other gunk in it.
If, after all that it still doesn't work, it'd probably be time to trundle off to a repair tech somewhere, 'cause anything else I'd do to it would probably be destructive instead of constructive!
AIR 2053 Current: 2006 Born Free 32 RQ Kodiak Chassis, & 1995 Coachmen B-van
Former Airstreams: 1953 Flying Cloud, 1957 Overlander, 1961 Bambi, 1970 Safari Special, 1978 Argosy Minuet, 1985 325 Moho, 1994 Limited 34' Two-door, 1994 B190 "B-Van"