When there’s an outage on League of Legends you’ll be one of the first to know on this page, as players will flood the internet to find out the problems, which would have occurred when playing the game on either PC or Mac. Usually it has something to do with the server going down, although there’s a few gamers that have mentioned login in issues in the past.
League of Legends Reports
@RiotSupport He is running it down on multiple accounts over the past 2 months ruining ranked after ranked for other people. It's hard to ban every account but maybe you contact twitch and get him banned for that behavior?