I can’t tell, the system is much much bigger than this. You can only debug it all. Try it on a clean project.
Maybe this is silly but if a user has multiple monitors, and you only display the game on one monitor, why not let the OS handle it and let the user set his main monitor in Windows?
As a user of multiple monitors I can give feedback that I use the secondary purely to display the stuff I don’t want to clutter my main, like logs. If for some reason my secondary was a game monitor or TV I’d just set that to my main for games in Windows.