Ok, so the fob and central locking module are responding at least, but it sounds like the pump isn't. Do you get a buzzing sound from the rear left when you try to lock or unlock? Does anything happen when you press the lock/unlock button on the driver's door?
There are two locking vacuum circuits. Its not uncommon to get a leak in one of them, but both at once is pretty unlikely so I'm thinking failed pump motor, or an internal leak.
Welcome by the way
