Unfortunately we are not mind readers, when asking a question its quite important to give make and model and year of caravan and or appliance so we might be able to identify it.
However as you are asking about a gas fridge, there are some basic questions.
is it a manual piezo spark generator that produces one spark each time you press it, or is an electronic spark ignitor that produces a train of sparks when the ignition button is pressed?
Can you hear it sparking?
Do have gas turned on? And do remember if the fridge fails to start its gas you should leave it at least 3 mins to allow the gas to disperse before trying again.
Is the caravan within warranty? if it is then you should contact your dealer who should be able to resolve it. If it isn't in warranty, only attempt a repair on a gas appliance if you are qualified, and have the required test equipment otherwise refer it to a qualified fitter.