My screen turns black whenever I get into loading screen PBE

This morning, I tried to get into an arurf game on PBE, and right when champ select ended and the game popped up, my screen just stayed black. I could not tab out but I could see my cursor. So I tried to shut down my computer, but right when I got back in it turned black. I tried to wait it out, but after ten minutes nothing happened. I then tried to get into a game of urf later in the day, and it did the same thing. Please help.