problem selecting your champion

When i enter a game , like ranked , it works , but after a match i entered again and i couldnt ban champions or lock in and it says : ''There was a problem selecting your champion. Please try again.'' And i got 5 minutes leaverbuster. I said ''ok'' . Not happening again. I waited 5 min then i got into a new match. Same problem then i got 30 minutes leaverbuster. PLEASE HELP ME I DONT KNOW WHAT TO DO !!!