Nissan altima trunk

Multi-possibilities. Could be actuator. Could be wiring. Could be striker position. Pretty much needs correct diagnosis. No way in advance to know which. Does is sound like the mechanism is trying to latch when you use the remote? If so, you might try the below. Otherwise, you face possibly changing the actuator or wiring. And that might get a bit involved. Which is why a proper diagnosis would help.

You can try to adjust the striker. There are two bolts you turn to allow the adjustment.

The striker assembly may be out of adjustment. This is the metal piece that the trunk lock assembly grasps when the lid is closed. These strikers usually have bolts that can be loosened allowing the striker to move up and down to obtain proper adjustment so the trunk will open/close properly

check your remote trunk switch

If after every re-adjustment the trunk close only to refuse to close after sometime, it is posible that striker is not tight enough and probably shifting after some uses. It is likely also that the threads on the bolts or screws are worn lightly. If posible try using a spring washer or some threadlocker medium strenght.

electrical trunk lid latch more likely broken if keep open release trunk.

if the latch is broken you need to get a new latch.

CHECK FOR LOOSE BOLTS AT THE LATCH STRIKER IF BOLTS LOOSE MOVE STRIKER TO CORRECT POSITION SLOWLY CLOSE TRUNK LID UNTIL THE TRUNK LID LATCH AND LATCH STRIKER COME IN CONTACT TO CLOSE TRUNK.ONCE BOTH ADJUSTMENTS CORRECT. TIGHTEN THE LATCH STRIKER BOLTS TRUNK SHOULD NOW CLOSE.

If you have automatic pulldown watch your fingers. If you hear the pulldown working the motor is good. If not the striker needs adjusting or the motor is bad.
Check the edges of your weatherstripping and if the hinges are rubbing inside the trunk.

If you have a manual setup look under the lid to see if the striker is loose and adjust. Sometimes the part in the trunk is the adjustable side.

YOU WILL REQUIRE DIAGNOSTIC TO DO THIS BUT IF YOUR VEHICLE IS LOCK IN A SAFE AREA JUST LEAVE ONE COMPONENT OPEN AND CHECK IF THE ALARM WILL SOUND AGAIN REPEAT THIS TILL YOU FIND THE DEFECTIVE COMPONENT.

If you took the trunk lid off another car and put it on your car, you are going to have to adjust the lock (the part on the inside of the trunk lid) or striker plate or loop (the part on the lower part of the trunk that the lock latches around). no two cars will have the same adjustment of the trunk even though the parts are the same. There should be bolts or screws that you can loosen (not remove) that will allow you to move the lock or striker plate/loop. If you take lipstick and put it on one side of the trunk lock and close the trunk before you loosen the bolts or screws, you might get an idea about how to adjust the parts to make them meet up in proper alignment.

Good Luck