Power locks will only lock not unlock.

Way to find out is have door lock system diagnosed with a scan tool. System is selfdiagnostic

Would recomend dealer they will have equipment. Not likely independent would invest in that type of tool. There are five modules that control door operation so gets a little involved

The first thing you need to do is check your fuses at the rear electronic control module. It is located in the trunck left side behinde the trunk liner.

I just want to make sure weare on the same page so I am including the wiring diagram and fuse location and what that fuse controls. Grab a test light and check that you have power on both ends of the fuse. Fuse # is 28 and it is the only fuse that controls the rear trunk and rear door locks and it alo controls your fuel door lock. Are yu having problems with that also?

See the diagrams below

Does the trunk lock properly and unlock when you use the remote? The trunk lock mechanism could be failing.

Check the lock and the adjustment of the slam plate, the lock may be triggering and not unlocking due to an adjustment problem.

Mark (mhpautos)

Yes, if you hear the actuator working in the trunk area but it does not unlock, then that could be failing already. Have replaced a few of them because they do go bad sometimes. Especially if it is when unlocking. Next time just use the key in the trunk and see if the lock actuator tries and fights you to lock back or vise versa, you try to lock but then it unlocks? If it does the trunk latch mechanism is faulty. Let me know what you find.