Tailgate doesn't shut. I used to have to slam the tailgate real hard for it to lock, now it doesn't close at all

I have had this happen twice on my Silverado. The first time, the rods (small rectangle shaped, not round) in the tailgate that stick out on each side as latches were gummed up. They didn't move freely in and out. When you lift the handle, they should retract inside the tailgate. When you let go of the handle they should pop back out. Mine would stick in when I lifted the handle so they didn't pop back out when I let go of the handle and didn't latch when I shut it. A good spray of degreaser and then a coat of lubricant fixed it.

The next time it happend, it wasn't gummed up or rusted. I had slop in the handle and lifting/letting go of it had no effect on the rods. It was broken springs and the mount that they connect to inside the tailgate.

If you just want to get it closed until you can fix it, (regardless of if it's gummed up or broken springs) this will take care of it. First, make sure the rods are not stuck out. If so, push them in on the sides of the tailgate. If they're just gummed up, you may need someone to lift the handle while you tap the rods with a hammer to push them in. Once they are in, have them let go of the handle and see if they stay in. If so, hold the tailgate closed and lift the handle a little and look under it (inside tailgate). You will see two vertical metal pieces. One on each side. These connect to the rods that run inside the tailgate and exit on the sides, which are what locks the tailgate when you shut it. Hold the tailgate shut and stick a flat blade screwdriver under the handle and up against either of those metal pieces and give it a whack with a hammer a few times. (Don't lift up on the handle while you do this, let it rest against the screwdriver). You'll see the metal strap move towards the side of the truck as you do it as it pushes the rods back out and latch to secure the tailgate closed. Then repeat for the other side/metal stap piece.

There are springs that control the in/out of those rods. On the backside of the tailgate (the side facing the bed) there should be a square/rectangle access panel right behind the where the handle is on the other side. Open it up and you'll see the parts. You'll probably be able to tell by looking at it what broke if it isn't just rusty or gummed up rods.

Hope this helps!

Check the tailgate lock rods behind the handle. The bezel around the handle pops off, and the mechanism is behind there. The rods that go to each side of the tailgate may be stuck inward. A little wd-40 or lubricant should work them loose again