Directly behind the key slot under the handle is a T shaped cam. It fits into a slot in the casting of the lock. If you lift the handle and insert and turn the key, that cam will rotate. All the mechanism does is stop the handle from lifting. When it does lift, the latch pin on the back of the cabin cover retracts. When the cover is closed, the latch pin on the back snaps behind a small bracket to hold the door closed.
Lite Tackle's picture shows all the detail.It also shows the key .
So , do you have key holes?
When you turn the key does it keep the handle from lifting?
Are there those clips that the latch pin hooks behind and are they adjusted correctly.
It's not rocket science