…So that you have multiple monitors going at once.
Maybe look in the system preferences on the gaming computer, if you can, to what the monitor settings are. Maybe it’s looking for a particular layout scheme with two or more monitors and the monitor you are hooking up with seconday monitor that doesn’t display unless the primary is also displaying.
(That’s a shot in the dark.)
Well, I have no way to look at the system preferences, but, I can try hooking up two monitors. With the goodies I have here I can connect to any combination of the 3 video outputs on the MB: VGA, HDMI, and DVI. OR, I can connect to VGA or HDMI and one of the two DVI outputs on the graphics card. I’d have to get another DVI cable to connect to two DVI outputs simultaneously. (I’ll look tonight inside the empty (somewhat smaller - more like an old 386 style “full tower”), never used gaming case we also brought back: I basically just used it as a box to stuff as many cables, drives, and so on into it as I could, but we were way too rushed for me to make an inventory.