Older fridges not working is a fairly common topic on our Eriba Touring forums - dealing with caravans that could be up to 50 years old or a bit newer for the fridge equipped models.
Likely causes, in no particular order:
1. Caravan fridges are adsorption type - and rely on heat (gas or electric) to force the working fluid around the heat exchangers.
If the fridge hasn't been used for some time, the crystal and liquid mix in the working fluid can separate - removing the fridge and inverting for 30 minutes - several times - can remix the chemicals and restore "as new" performance
2. The older model Electrolux fridges needed to be accurately levelled - within 2