I installed DaVinci Resolve 12.5 and when I launch it, I get the splash screen, the login screen, the project manager, but then, it disappears. It is still here in the Windows taskbar, but it's nowhere on the screen. I suspect it creates a fake second monitor and displays there.
When I open my monitor settings before launching Resolve, it shows only one screen (1680*1050), and after I launch Resolve, there is a second monitor (disabled) which says 'No other display detected'. In the display section of that second monitor, I have 'Available display output on : [My card]'.