this could be a couple of things.
1:. child safety lock jammed or
2:. central locking malfunction.
when I had this problem I first added wd40 oil then put the key in the lock of the sliding door and just kept turning back and forth until the latch released itself, keep trying to pull the door open with each turn of the key. if this dosnt work let me know.
Rodney
December 2007