On this page, you will find more information about the most common causes and most relevant solutions for the League of Legends error 'Unexpected Error With Login Session'. Do you need help straight away? Visit our support page.
The Riot Games documentation indicates that error code 'Unexpected Error With Login Session' is caused by the following problem: "The login session error tends to arise when another instance of a League client gets stuck running in the background.".
Do you think there is another cause for this error? Let others know in the comments.