When I installed my DDIN, I goofed and didn't plug in the switch in my glove compartment (it was getting dark and I was sooo dang thirsty), which resulted in me being utterly confused when I couldn't pop my trunk on a grocery/beer run that night. My point is - the default when the glove-box switch is not plugged in is no trunk access. Since this is a new car to you, and esp if there is an aftermarket stereo installed, maybe start there.

Another idea is that if you can pop the felt trim on the trunk lid from inside the trunk, you may be able to get to the cable that the safety pull is usually attached to. Maybe check your fuses, but I think the trunk is controlled by the BCM, which also controls seats (among other things), so if you're having problems with moving your seats forward/backwards, you need to look there. I have read that water can get channeled in and fill the battery compartment where the BCM is and cause all kinds of weird issues.

Once you manage to get your trunk open: if you aren't sure why what the problem was in the first place, check your wiring loom where it passes through to the trunk. Its common enough for the wires to get pinched and fray or break there.

G'luck and welcome.

 

Yep, probably broken wires in the flexible wire conduit at the hinge point. Fairly common issue. You will need to disassemble your trunk components from INSIDE the trunk through the back seat, then the latch can be manually opened. If there is even a little bit of the existing safety cable still attached try to grab it with a pair of pliars and pull on it.