There's a trouble shooting guide and several other documents for Suburban heaters in the FRF Library. Here's a link to that guide. http://www.forestriverforums.com/for...do=file&id=119
You don't say how old your RV is (please consider adding all of that information into your Profile), but it most likely has direct spark ignition (no pilot).
The usual sequence of events is that, when you turn the thermostat on, the blower starts and if the furnace senses enough airflow, it turns on the gas and starts sparking. (You should be able to hear and smell that outside at the heater vent.)
If it doesn't lite, it will try about three times and then lock out. Turn it off at the thermostat to try again.
You may just have air in the gas line so try a few times (assuming you are hearing that spark).
Let us know what you find/hear.