The locks are pneumatic, perhaps the hose has fallen off it's connection with the pump or the lock.

In the SRT section, you can download the service manual and start investigating this. The Pump is on the passenger side behind the stop/tail/turn light assembly. Depening on "Coupe or Roadster", the process of getting to the pump varies.

Same goes for the lock, to get to it in the Roadster is easy, but I've never owned a coupe so I don't know about how to get to it on those

Now that I think about it, I almost remember something about the lock giving trouble on the Coupes before. Try putting "lid lock" or "trunk lock" in the search box here and see what you get.