It sounds like it could be an electrical issue, like a loose or mouse-chewed wire. Perhaps try changing the spark plug and check the plug’s electrical connection.
You may also want to check the oil level. There’ could be a sensor that won’t let it run if it’s low on oil.
You can also check the air filter. Even you can just remove it to see if it will start without it.
I had a problem with mine. The neutral line that connects up in the distribution panel got fried. I don’t totally understand it. But I learned that a lot of older RVs that are only 30amps can have this happen. You could check there to make sure all your wires look healthy and safe. Best of luck!