Does the fridge have a Piezo spark or an electrical spark?
If you have a piezo sparker you could ensure the sparker and the wires attached are all connected and not damaged. If they are, the problem could be the failure of the complete piezo module. There is no battery that can be swapped out and the entire piezo module may need replacing.
If you have an electric sparker, check the sparker and the wires attached are all connected and not damaged. If they are, the problem could be no or too low a voltage from the leisure battery, or maybe there is a separate battery that needs replacing.