how can i get my central locking working on my T reg vauxhall vectra estate?

hi, i been having a problem with my T reg vauxhall vectra estate 1.8 16v ls central locking, i brought a used one for the drivers door on ebay for 15 pounds. when i press the button on my key i can hear clicking and the indercater lights flash but nothing happens, befor when i locked the car with the key the windows used to close automatic but doesent now since i fitted the new one,
the one i took out in the drivers door had a crack in it and looked like its been tampered with so i thought it would have been that but its not.when i open the petrol flap and look at the lock that works with the central locking when i press the button on my key i can see the pin moving about 2mm back and forward but thats not enough to secure the flap, i tryed putting the key in the ignition and turning once till the lights come on and pressing the lock and unlock button, but i just read some said leve the door open , i dont think i left the door open, dont know if it makes a difference but will try it in the morning. anyone please help,