Make sure you have LP in the tank. Make sure the valve is open. Make sure critters have not made a nest in the combustion or exhaust ports. Dirt daubers love those spots.
The fan will run for a half minute or so before the control board turns on the glow plug and opens the valve on the burner. If no ignition occurs, the system will shut down and you need to have the system serviced.
Bob & Joan Alexander, 2010 Tiffin Phaeton 36 QSH, 2013 Jeep Wrangler (toad)
Lobo & Juniper (woof, woof)