2002 nissian frontier tailgate is stuck

First thing: Try using the key to move to the locked and then to the unlocked position. If this works, open the tailgate... This also pretty much tells you what the root cause problem is, which is a pressed-in plastic post working its way out (see below).

If no bedliner, just remove metal plate inside tailgate and actuate by hand inside to open. If bedliner, first use a small screwdriver to carefully (don't scratch paint) push in latches at either side of tailgate to open/lower tailgate (if locking/unlocking as above did not work to lower gate and gain access). Next, use two blade screwdrivers to pry out the "buttons" that hold the ends of the tailgate liner where they wrap around the sides, then remove bedliner piece and metal plate, etc.

Once you have access to inside of tailgate, you will see how the mechanism works by pulling up and down on the handle while observing. You will probably find that the slide mechism that locks and unlocks the mechanism has been allowed to move such that it cannot unlock/allow movement of the latching mechanism. This is usually the result of the pressed in plastic anchor being worn/loose. I had some success with cleaning thoroughly with alcohol or brake cleaner, allowing to dry and then using super glue to hold it firmly in all the way. Still have to hold handle up when closing gate and keep key on hand to unlock every time opening, but it was a free repair...

I just had this same problem. I had a tonneau cover on and couldn't get the tailgate down. What I did was got to clothes hangers to push in the latches on the sides of the tailgate. Its really simple. Now as for the lock, I just decided not to lock the tailgat anymore. I took a zip tie and wrapped it around the slide that locks and unlock the tailgate. Don't make it too tight or it will not open at all. Leave a little slack for movement and it will work for then on. Just remember you cann't lock it anymore. Mine has been like this for more than a year now and still no problems. Just can't lock it. Hope this helps.

Tailgate on 98 nissan stuck