Rear deck latch will not latch

There are a couple of things to consider. First, if this is a standard latch mechanism, there could be a spring missing in it. That spring rotates the hook that does the latching to the bar on the underside of the trunk lid. That hook could also be rusty. A squirt of Mopar Spray White Lube works well for that. It goes on rather watery and soaks into the tight places. The juice takes the grease with it, then the juice evaporates and leaves the grease behind.

You may also have an electric soft pull-down latch. When you pop the latch, you'll hear the motor run for a couple of seconds as it raises up the latch. To close the lid, you only lower it gently until the latch catches it and pulls it the rest of the way closed. If the fuse is blown, the latch will not extend, then that can make it hard to slam the lid enough for it to latch. You have to slam it hard enough to compress the weather strip.

You can use the shank of a screwdriver to mimic the bar on the bottom of the trunk lid. Use it to push the latch down just like the bar would. You might see another lever rotate and snap into place to lock the latch, and you will hear it snap if it is rotating freely. At that point you have to unlock it before it will work again.

If you have a standard latch, someone may have adjusted it down too far, so now the lid has to be slammed really hard to get it to latch. A potential clue is the weatherstrip around the trunk opening is chewed up from being over-compressed, or, if it is only damaged in one area, someone may have damaged it, then over-adjusted the latch to compensate and stop water from getting in.

You can get better advice, usually for free, from the people at most body shops. They are specialists at adjusting latches, and addressing wind and water leaks. To be safe, visit a shop during their lunch hour. Most employees are paid by the hours they have on a job, and prefer to not be distracted during those working hours.