I cant see my screen when i go into game

Ive lost 2 ranked games now cause i couldnt log into the champion screen or game it keeps doing well when i first log on but after a while it just dosent want to work anymore therefore making me lose 2 games it happens everyday i uninstall the game and try again but still does the same thing i dont know how to fix the problem and hopefully i dont get ban for my consecutive losses thats been happening

Need help

Kind regards

Norbit