[200_S_AWD]

Welcome to the forum. Is fuse #38 under the dash OK?

Does the dash button and trunk button feel 'normal' when you push them (they spring back when you release them)?
If a switch is shorted 'on', the system will time-out and be inoperative. It will also store a 'Stuck low' in the BCM.

Can you lower the rear setback, crawl in and release the trunk lid emergency release handle? After doing this, does the 'trunk ajar' warning come on?

 

[200_S_AWD]

Can you get in the trunk via the rear seat and pull the emergency release handle while pushing up on the lid?
It may have a mechanical sticking issue if the actuator doesn't 'pop'.
Maybe something stuck in between the latch & striker?

 

[200_S_AWD]

Back to the wiring diagram in post #2, the Beige/Yellow stripe wire should have a momentary +12 volts when either trunk release or key fob button pushed (twice).
The actuator needs a good ground to the sheetmetal. Electrically, it all seems intact if the trunk ajar lamp flashes, the latch dog just doesn't seem to be able to release itself from the striker.

Is there a mechanical binding at the latch mechanism? Were the old washer marks used to position the latch in the original position after the actuator replacement if you removed the latch?
With the trunk lid open, latch the latch and see if it will power open? Lubricate, straighten or replace the latch as necessary.

 

[200_S_AWD]

There should be 3 ways to electrically pop the trunk:
1) the key fob button (press twice).

2) the dash release button.

3) and a 3rd one hidden under the trunk lid.
The external release switch located on the underside of the decklid overhang. The release feature will function only when the vehicle is in the unlock condition.

None of these buttons should feel funny and have a good tactile spring-back.

The next step would be a scan tool to see if the BCM is storing any codes related to the trunk release. These aren't OBD2 codes, so an advanced tool that can read Body codes may be neccessary.
B181C-23-TRUNK/LIFTGATE INPUT - SIGNAL STUCK LOW
B1828-64-TRUNK/GATE RELEASE CONTROL-SIGNAL PLAUSIBILITY FAILURE

B181C-23:

Let us know what you find.