Should be a gas stove and not need any generator for use. They do draw some 12v power, especially at startup, but after that, they are very power efficient.
Some Wallas stoves are designed for kerosene and some for Diesel. If you call Scan Marine they will tell you to use what your stove was designed for. Scan Marine is very helpful if you have a problem.
I would drain out the old fuel and replace with new. Read the manual carefully. Reset the stove by removing power temporarily by removing the fuse. Make sure all fuel lines are tight. It takes a fair amount of voltage to start so be sure your battery is well charged. When are battery gets below about 12.4 volts I start the boat motor to get the voltage up. Uses a lot less power when running. A Wallas is usually powered off the starter battery directly. Always start and stop on highest setting. Try to use it at least once a month.