This game gives my monitor no signal?

When I start up a game of LoL, as soon as I load into the game my monitor says it has no signal, but does when I tab out

This happens with no other game I own on my main monitor (1440p), and LoL works on my second monitor (1080p) fine

It's really odd as when I tab out and hover over the game icon at the bottom, it shows me in the game and any messages I type. Super odd bug, only started happening today, and happens every time I open a game even in practice tool