Gas furnace doesnt lite when turn on.what could be problem?

Check the owners manual for directions https://www.manualslib.com/

If the furnace made a clicking noise trying to turn on and then makes the BANG noise at the furnace, it’s most likely a delayed ignition. Imagine a room full of gas and then someone decides to light a match. Big problem. That's what’s happening in your furnace if the ignition of gas is delayed.

A variety of issues can delay the combustion of that gas. So the gas builds up in the furnace until—BOOM—it ignites, causing a mini-explosion. This can harm the heat exchanger, which is very expensive part to replace. Some causes of delayed ignition includes:

1. Dirty burners
2. Flames are lifting away from the burner outlet due to too much primary air
3. Too much gas

If you're handy enough to understand what I've said then burners can be cleaned/replaced, and primary air can be adjusted. With some units gas flow can be adjusted as well; other times the gas valve will need to be replaced.

If you've no idea what I've described, GET HELP before you ruin the heat exchanger and have a more expensive problem on your hands or worse...

This is either a problem with the spark igniter or the circuit board. Here is a link to all of the spark electrodes for Suburban:
http://suburbanrvparts.com/furnace-parts/furnace-parts-by-category/spark-electrodes/
Here's a link to the circuit boards for Suburban furnaces:
http://suburbanrvparts.com/furnace-parts/furnace-parts-by-category/module-boards/

Clean the flame sensor not the igniter . check air filter is clean .

If I recall correctly, model number Rheem furnace you listed has electronic ignition to light the pilot, when the home's thermostat calls for heat. Is this what you're having a problem with?

Sounds like your gas valve is sticking. Your repair man is somewhat correct by meaning that the furnace will attempt to start 3 times before going out on "Lock-out". The furnace is reaching it's expected life and you will start experiencing more frequent issues with it. Check into some of the incentives to get a replacement with a higher efficiency rating. The newer units have greatly improved in performance as well as comfort.

check ur venting first make sure its not plugged

Check the pilot light size. Is it small and not surrounding the top 1/3 of the thermocouple? If it isn't then the pilot orfice is restricted or the pilot tube compression nut could be loose. The pilot gas adjustment screw may also need adjusting if this gas valve has one. These problems should only be addressed by an experienced service tech.

You more than likely need to change or adjust your thermocouple in the furnace. It is the part the pilot light heats up to let the furnace know it is safe to turn on the gas flow. These go bad over time and are fairly inexpensive and easy to change.

i HAD THE SAME PROBLEM, TURNS OUT IT WAS THE FLAME SENSOR, CLEANED IT, AND ALL WAS GOOD