Keyfob doesn't work
 

Hi all!
I have a '92 300SL-24 valves and I can't get the keyfob to work. I have replaced the batteries and have tried all the synchronisation procedures I have seen, but I can't get it to work. All of the locks work and the central locking works too, if I close it wih the key, all of the lights from the handles flash, but I can't get the remote to work. Does anybody have a clue on what could be wrong?