The symptoms you describe could be a poor electrical connection where the pump plugs into the side of the caravan. This isn't uncommon, and can usually be fairly easily repaired.
You haven't told us the make or model of your pump system, but most have a pair of brass pins and sockets in the pump connection, that make the pumps electrical connection. These can become corroded and/or slightly bent with the continual insertion and removal over time.
Pull out the plug and look for two brass electrical connectors. The pins are often of a split design, but over time the gap can close a little which prevents them from making a good contact in their respective socket tubes. Gently prize them open just a bit so they make a good contact when they are pushed into third sockets.
If the look very dull or have any powdery deposits (usually green), try using a proprietary electrical contact cleaner on them. If you don't have any of that, try some vinegar on a cotton wool bud, but make sure you wash the components afterwards.
If that doesn't sort out the pump, then its likely the pump it's self may be faulty. If you're lucky there may be another caravanner with the same system on site, and perhaps you could ask if you could try their pump or if you could test your pump on their caravan.
If the pump is faulty you will need to replace it. The simplest is to buy a complete pump and hose of the same model, but as your abroad that may not be possible, so with a bit of care you should be able to dismantle your pump from its hose, and to fit any similar pump you can obtain, it doesn't have to be the same make. Just a heads up, when removing the old pump, disconnect the pumps wire from the plug, but attach a piece of string to it, so when you pull the wire out of the hose it pulls the string through the hose. You can then use the string to pull the new wire back through the hose. Washing up liquid can be used to lubricate the cable to help it thread through the hose. Rince some water through the cables side to remove any residue.
Hope this helps