Cant play in full screen

Not sure what is going on. I just played less than 24 hours ago in full screen mode and have changed literally nothing on my computer. After champ select, my monitor disconnects. I've tested other games and they all work correctly. I know its not a hardware issue. I can hear when the game starts and the sound continues to work. After a lot of research I found a solution to press alt+Enter to go into windowed mode. This did fix the problem of the monitor being disconnected, but did not fix not being able to play full screen. I tried switching back into full screen mode while in game and it disconnects the monitor again. I saw a lot of problems people had in patch 7.1, but none as of recent. Is anyone else having this problem or know how to fix this? Any help would be appreciated.