Door Lock Issue

[E986]

Hello all, hoping someone can assist with a door issue I'm having. The door doesn't lock manually with the key, or with the remote. When I hit the remote button to "lock", I get one beep, but the doors stay unlocked.

Looking through some other threads, a couple items that could be relevant and/or may provide more information: the window does go down when pulling the door handle, but immediately goes back up when you release it; there is an aftermarket cd player; and the door panels themselves are obviously not original (I have mostly gray interior yet the door panels are black).

Any help with the issue is much appreciated!