First, the obvious questions.. Gas is turned on? You have gas in the cylinders? Auto switch over lever to full cylinder? Purged the gas lines before trying to start fridge on gas?
I know that if mine sets for a couple of weeks, with the gas off, when I turn it on, it takes a minute or so for me to get the stove top burners to light! I turn on the hood fan, turn on the center knob and hold the clicker until it lights. Then I turn on the others and let them run for a minute or two.
Then I light my HW tank. It might take a couple of tries to get it to fire (end of the gas line).
The fridge is in the center of all of this. After the HW lights, the fridge will usually light on the first try.
If all of the above checks out, see if you have a plugged up flow tube for the flame to get air from.
Good luck!
Mitch
2013 F150 XLT 4x4 SuperCab Max Tow Egoboost 3.73 gears #7700 GVWR #1920 payload. 2019 Rockwood Mini Lite 2511S.