My trunk will not latch

First, is it an electrical latch that pulls the trunk lid down the last inch or two or is it a mechanical latch that grabs when you physically push the trunk closed? If it is mechanical, see if the latch was accidentally tripped. Use your key to do this by inserting it in the lock, turning it like you were unlocking the trunk and helping the latch bar to move to the open position. If it is electrical, you have probably broken on of the trunk lid motors and will need to replace one or both of them.