Heater wont work

In addition to what's been asked, what did the dealer tell you to do already?

Just another tip. Before you go running off to the dealership.

There is a 'DELAY' built in on the RV furnace and ac.

If you have been turning it "on and off and on and off". Its' cycling between delays and It will NEVER start.

It's not your house furnace! You are not giving it enough time.

The delay is very long on some RV's. Let it sit for an hour then turn it on and WAIT for the furnace to come on. It does seem like an eternity but wait it will come on.

My delay is so long that to this day 10 years later when I flip the ac on and when it doesn't come right on I still sometimes think oh my god it's broke.......then it turns on.

Albeit your dealership should have told you this but my guess is they didn't. :W Good luck I hope all goes well.

when you turn on the main propane tank,turn it slow, theres a built in safty that will trip if you did it fast.and must have good 12v battery weather on shore power or not.

A description including brand and model number plus what it does or what you hear may be a wee bit helpful.

Based on the info given, it could be about 999 different things.

Yes, need more details please about the type of camper, furnace, the problem, and steps you have already taken.

There's lots of knowledgeable folks here willing to give you suggestions of things to check, just need more details from you, please.

Are you talking your "furnace"?
Is gas turned on?
Is thermostat turned on? Small switch on some.
Does the fan start?
Are you connected to shore power or running on battery power?
Any noise from unit?
Make and model of "heater"
Do other propane appliances work?

What does s the brand and model of heater?