The tailgate on my 1999 Mazda B4000 Troy Lee Edition (essentially a Ford Ranger) will not remain shut. It is not locked in the upward position like the youtube videos you find talk about. It does not look like the latches on each latch assembly reach the square metal piece they are supposed to fit into to stay locked. One spring appears to be loose, but the other looks fine. The rods and plastic pieces look okay as does the handle (probably). Any ideas on how to fix this?

 

Does the tailgate look flush with bed when its up, could be lower hinge is loose or worn down

Its a pretty simple mechanism for the latch, similar to any home door latch setup
A latch(on door) and striker plate(on the frame of door)

These need to line up so latch can go inside striker plate's hole and then the spring in the latch pushes it out all the way inside that hole, this holds door closed or tailgate up

If tailgate is not sitting flush to bed then latch and striker won't line up
Striker plate is adjustable, a bit
Or latch is
But if this is a new symptom then something has shifted in the tailgate or bed to cause the mis-alignment