When I go to kbb.com and go to check my car's value it only shows Model S as an option for a 2016 Tesla. How did you get it to give you a value for Model X?
I had the same problem. However, if you Google "Kelley Blue Book Tesla Model X", one of the links (usually NOT the first one) will be specifically for a KBB Model X screen. Keep in mind, though, that the numbers it gave me were (in my opinion) inaccurate.
2016 Tesla Model X - Kelley Blue Book
Mike