on the '99 (I think thru '01..) it's a mechanical release from the cabin. Electric release from the keyless remote. Problem that typically happens w/ remote is cable gets frayed in trunk (easy DIY fix w/ a wire ferrule or the like . If you hear the motor release but nothing happens, that will be the case w/ the remote.
If the mechanical level on driver's sill doesn't work it could be a couple of issues. Most likely, the mechanical lock for the levers (both trunk and frunk) is not moving to the unlocked position when needed. (PS it only works when the door is open too but I hope you already knew that). If it's not freely unlocking, you can use a small screwdriver and manually slide it to unlock but slipping the skinny blade down between the frunk and trunk levers and sliding it parallel to the bumpers.
Try that and report back. You can also search threads here for manual rear trunk release to find more posts as subject has been covered before.
Good luck
