My game won't load (Mac)

Please help me out here team I have a Mac and my game won't load after champ select. As soon as the process of loading into the game starts after champ select, my screen just remains black and I can't even move my mouse during this process as well. won't even let me exit out of the game. Tried to reboot my laptop couple of times and also upgraded to High Sierra to see if that helps. Still having trouble loading into the game. Help a fellow summoner out here :)