Urgent Remote locking help????

The key remote for our 1998 Xsara, .18i has decided to give up the game. I have replaced the battery but am not able to reset the key?? Tried the ignition metheod suggested in the Haynes manual but to no avail. How do you have a key checked? It is the Rf type remote with no LED indicator lights at all and the only tell-tale would be the indicators flashing?? Do we just go back to Citroen?