Theres a micro switch on most that shuts off the monitor when closed...most of the time thats what causes these issues, easy fix cheap fix for the most part that you can do yourself. (I fixed a buddys in 10 minutes)
BTW..HP is only good for one thing..PRINTERS. every other product they make (or just put there name on) sucks donkey balls
In the future just stay away from there products.