I understand . been there; done that. makes no difference. I think the probleme is a generic microsoft video driver that overrides my ati video card in Windows 10.
Nvidia? SLI? I had the same problem. Uninstall your driver(s) and reboot. I let the GeForce Experience install the drivers and it then worked, but that's only for Nvidia. I understand that you have an LG monitor, but what type of GPU?