Why can't I login my League of Legends account?
1: Check region settings and the server status
Open the League of Legends client. ... If you are still unable to sign in, check the server status, here. If the server is up and running, try signing in again. In case the server is down, wait for some time and give it another go.
How do you fix something unexpected happened while trying to create a lobby?
While there's no surefire fix for the error, a relatively reliable workaround involves disconnecting from the internet, making sure the client registers you as such (by attempting to reconnect), and jumping back in. With a bit of luck, you'll be able to go through with creating a lobby and getting into a match.