Have to get a new trunk latch mechanism, I believe. If you have the auto trunk opener, sometimes when the motor dies the mechanism "sticks" in the up position, which won't allow for latching. Also, there is a lot of plastic in these and if the latch piece gets cracked, it can cause the same problem.
I had the same problem. my trunk was slammed toe hard and the metal bar that the latch latches on to got pushed down. if you connect a chain to it and pull up with force it should be put back into the right position and be able to latch
Mark's answer is the best. The latch certainly isn't robust enough. In fact, I bent mine back with a breaker bar. I had a cavalier a few years ago, and the body of the car rusted out right were the trunk latch connected. With some pop rivets and the right "magic" words I was able to make it last a few months until spring!
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