Door will only lock when door is open?

You would usually use the correct key.

Is it the lock button on top of the door or the latch that holds the door shut? If its the latch just pull door handle then flick catch back round with a screwdriver. Its a C lock that spins round...

Slide the card through the slot where the lock is by the door. Set the card where the lock would be. Now open the door.

The "door" that was opened was the access to China and all of it's trading ports.

A key is the preferred method. Without a key there are a couple of options: Break it with brute force Remove the hinges from the door (works 50% of the time) Pick the lock