UPDATE 6:00 PM - The issue appears to be resolved. Ranked has been re-enabled.
UPDATE 4:30 PM - We're seeing packet loss occurring on parts of the internet that are adversely affecting player's connections to the League servers. We're looking at ways to get around this, but for the moment we're keeping Ranked offline while we continue the investigation.
UPDATE 3:30 PM - We've identified the issue and are seeing improvements to player connections after initial resolution attempts.
There appear to be major connection issues ongoing right now making it impossible to login and kicking players out of the client. Issue appears to be worldwide. We'll keep you updated on the progress of the issue.