Newbie with some questions

Hello all. I just got my first RV a week ago and have a couple of questions. First off I have an 88 Cruise Air II that I currently have plugged into land power/water etc. My first question is this: I turned on the hot water switch 2 days ago and could hear the water heater going outside and the water got hot and all was good. The water heater light switch would come on and go off as I used water. Last night I noticed that the light was staying on and now I don't have any hot water and it doesn't appear that the water heater is coming on outside. I am able to turn on the stove w/o any problem so I do have propane (1/2 a tank). Any ideas? My other problem is this. The toilet valve that you step on to flush the toilet was leaking and I replaced it with a new valve. Now no leaks. I seem to have very little to almost no water when flushing the toilet now. I have good water pressure from all the sinks and the thing leaked really well before I replaced the valve. Any ideas on this one? I appreciate all your help and look forward to many years of RV enjoyment!
Newbie with some questions

For the water heater, it could be as simple as a failure to ignite for some unknowable reason (dirt, odd breeze, etc.) and the safety control went into lockout mode. To test this idea, shut off the power for a minute or so to reset it and try again. This is not uncommon with electronic ignition systems of that vintage. could also be a dirty flame sensor, but at this point, you need someone who is familiar with these systems to assure that it is repaired safely.
As for the toilet, did you crimp the water line? Or get any crud in the valve while installing it? Both very easy things to do and easy to check for.
Good luck, Ed