Just want to get back to this issue, If I use 2 monitors login screen shows normaly centered, If I use 3 monitors (1 is 4k resolution, two are full HD) it shows the screen minimized and I have click on it in taskbar and hit Windows key plus arrow up to open the login screen.
Just ran into what I think is the same issue, initializing window was a light gray and log in window was invisible. I just reset the gateway trial and relaunched the designer successfully. Not sure if it was a coincidence or something. Gateway is on 8.1.48