2005 Pontiac Grand Prix Door Locks will unlock but wont loc

I have a problem with my locks then I turn the key to unlock all the door they all unlock. But when I try to lock them just my drivers door locks but all the other ones dont. Usually you hear a click from the mechanism when its trying to lock them but I dont hear anything. So I tried locking from the inside what I heard was a small click I wasnt really sure if it was coming from the fuse box from the side or something but it was still not locking the doors. So I tried unlocking them from the inside and it unlocked all the doors so I am not quite sure what the problem is can anyone help me? Rgiht now I have to go to each door to lock it manually which is a pain.