Hello Graham,
If the fridge only stopped working on one fuel, but was ok with the others then that would point to the system associated with that fuel, but as it has stopped working on all fuels, that points to, or something like the grill covers being left fitted and preventing the condenser side of the fridge getting enough cool outside air , or more seriously a loss of refrigerant fluid.
This needs to be looked at by fridge engineer. In some cases the leak can be fixed and the system recharged, otherwise its bye bye fridge.