2 screen with win10

Hello,

hi i have a elite desktop 800 g1 ssf wich has a regular old parallelogram place to plug a display and a hdmi place with a parallelogram adaptor.

my may screen work on both holes

i have 2 other display one is benq fp71g+ and the other is a dell from 2007 . last month i was using 2 screens (win10 64)
i dont know what happened but only on screen shows up.

when in windows if i open display and then plug the second screen , the display window is catapulted on the other screen ( black) so i cant acces the display and ask for detection.

What can i do?
i tried restarting the pc with both screen on but i only have black screens and i have to unplug a screen to have a screen appear on my regular monitor.