The laptop doesn't even seem to find a second display. With the one's that don't work, what's basically happening is that I connect the TV via HDMI output but the screen remains blank, as if nothing's connected (completely blank, not just black). The issue is that some of the laptops are able to use dual displays via their HDMI output with a TV, and some aren't. So a client has a few new laptops, purchased together, all the same model: Dell Latitute E5520.
