Confirm that the switch for the fridge is on and that your leisure battery is equal or higher to 11.5v
Please bear in mind that the fridge is the first feature to stop working when the leisure battery reaches a value between 11v-11.5v
If your fridge looks like the one in the photo below, also make sure that the cable is properly connected and that the button is on high or low (it should have a yellow light on "Power" if the fridge is on).
Other relevant articles:
How to use the fridge
How to monitor the leisure battery level