When it comes to the "clueless" asking for help like; "The generator won't start", there is some basic help we can give short of "mind reading", or asking for brand and model of generator.
Is the battery dead? Check voltage (need about 12.2v or better).
If you have voltage @ battery, did you connect the battery (disconnect switch)?
Check to see if circuit-breaker is tripped? Turn it off and on to reset.
Check for a burned out fuse. They are cheap so just replace it.
If by this time they have not replied with "now working", or given us the asked for information, they are in no shape to handle more involved repairs.
After about a week and no reply the best advice for them is:
"Take it to the nearest RV service place to have it serviced".