PVC door wont shut (or lock)

[Trying2bHandy]

Hi guys

I have a PVC patio door and it wont lock.

The full story is that it wont shut, or it will shut, but only to the point where if you push the door it will open i.e. the catch isn't engaging. There's nothing that SEEMS to be jamming it. It just isn't catching.

I think if I can get the catch to engage then I have a hope of getting the door to lock whilst I call someone out to propery fix / replace.

Any ideas that a noob can do in order to get a locked door?

Sorry / thanks!

 

[crank39]

Is this a sliding 'patio door' or a pair of 'french doors' firstly