UPVC door locking problem

[tg100]

Hello there. I had a look at some old threads but didn't see any that match my problem locking an external upvc door.
The trouble is if you shut the door, lift the handle up to engage all of the bolts/ hooks/ sliding bits; then you try to turn the key it just won't turn. If you try this with the door open the key turns easily and the deadbolt comes out. I tried taking off the metal plate where the key operated bolt goes into and it was the same. I put some plasticene in that area and the key operated bolt made no impression in it so it seems the deadbolt key mechanism isn't allowed to operate when the door is closed.
Does this sound familiar to anybody?
Any suggestions would be gratefully received. Thanks very much.

 

[crank39]

So it looks like the deadbolt won't engage its slot, sounds like the door has dropped, either wind the door up a couple of mm on the hinges OR lower the striker plate down half the width of the screw hole

 

[Alarm]

Just about every uPVC locking issue posted here is this.
Suggest you look a bit harder.

 

[tg100]

I finally got around to having a good look at the door. Taking one of the plates off the second door that the hook goes into when you lift the door handle up seemed to allow me to lock the door. Then I could see the doors weren't close enough for the hook to engage in this plate properly. Playing with the allen screws in the hinges allowed me to move the doors close enough together for everything to function normally and now the door is locked!