Dual Monitor Problem. Main monitor black screen when both monitors connected but works fine otherwise

[join213]

Edit: Solved the problem by switching main monitor to HDMI and second one to vga. Still not sure what the source of the problem was but both screens work now so I'll take that as a win.


I have 2 monitors a 4k Asus main one and a Hp 1080 one as a secondary set up as extend display.
The Asus is connected with a displayport cable and the Hp is connected with HDMI both of them are plugged into the GPU.
This set up has worked fine for over 2 years.

My problem started when I opened a game that had a low resolution set and made it go full screen. When I did this the entire main monitor switched to the low resolution. After switching it back to the 4k resolution the screen went black but does not show "no signal". The second monitor works fine during this and the pointer can be moved between the black monitor and the second one and programs will load onto the main monitor as if there was no issue. The main monitor shows the bios screen on boot and the bios menus work fine but as soon as windows login loads the screen goes black.

I have tested both monitors individually and they work fine on their own but as soon as I try to plug in the second one regardless of which one is connected first the Asus screen goes black.

I'm stumped as to what the issue is and would love some assistance. Feel free to ask clairifing questions.

Specs:

Monitors
Asus P287Q - Display Port
HP 23er - HDMI
Motherboard: Asus ROG Maximus X Hero
CPU: Intel Core i7-8700K Coffee Lake 6-Core 3.7 GHz
GPU: Two Nvidia Titan X with SLI bridge
OS: Windows 10 Home

 

[popatim]

If the black monitor is showing the mouse on it then it sounds like you are viewing a black background to me. Does the mouse change size when you move from the 2nd monitor to the black one?