You need to rephrase your question so we can understand but I'm gonna take a stab at it. I assume you are referring to the WH not working. Are you trying to use gas or electric?. If it is a Suburban there is an outside switch lower left corner. If you tried to use 120 volts with no water in it you burned out the heating element. If on electric there is a circuit breaker in the power box that may be tripped. Were you using gas and run out? Many reasons and to little info.
try again with year make and model of you RV. Trailer, 5th wheel, Motorhome etc.
When someone says "my rig" in the RV world they are usually talking about their RV. When they say "it won't start" they are talking about the motor in a Motorhome or a generator.