remote locking wont work, kangoo 2002 van?

hi i seem to have a problem with the remote central locking on my kangoo van its a 2002 1.9dci{1.5}. the remote just stopped working,so i got the battery changed in the key still doing nothing,ive been searching everywhere for over a week about this problem.the doors will lock with the internal switch next to gear stick and use the key to lock drivers door.please help ive tried all the sync methods with no luck.