[rudeney]

You have a bad latch. It's likely leaking from cracks in the plastic housing where the pneumatic system operates. Sometimes what happens is the leak causes the PSE pump to run continuously so it shuts down the trunk circuit. If this happens, the mechanical part of the latch will work, but the pneumatic pull-down won't function. You may be able to get it working by pulling the fuse for the PSE pump to reset it. It's fuse 71 on the rear panel. If that does get it working, you need to replace of fix the latch. If you want to DIY, you can seal it with epoxy. Also, if the diaphragm is leaking, it can be sealed with epoxy or you may be able to fashion zip ties to hold it together as I did (ignore the bailing wire and solder - that fixes another issue):

 

[rudeney]

@tonylinc: If you don't have the powered trunk open/close option, then the Lift-O-Mat struts on the trunk are likely work out and need to be replaced.