You hear the trunk lock solenoid operating when you work the remote trunk open button in the car, try banging on the trunk lid while you get a friend to press the "open button", also try prying the trunk lid with a screw driver while operating the remote open button. Something is jammed in the trunk lock. I am sorry I don't have instructions to remove the rear seat back, but you will have to remove the rear seats, to gain access to the trunk, crawl in and remove the bolts securing the lock in order to see what it broken or getting jammed. I will add seat removal instructions as soon as we have an I30 in our shop.