If your League of Legends Client pops up with this error code: "There was an unexpected error with the login session. Please try again." Use these steps listed below to fix it!
- Press Alt+F4 on the client and click "sign out" not "exit".
- Press Ctrl + Shift + Esc to open Task Manger and close all instances of RiotClientServices.exe and all instances of LeagueofLegends.exe
- Reopen the League of Legends (or Riot Games!) Client and log in again.
If you are still experiencing some issues, repeat these steps and also close the program "KillerServiceNetwork.exe" as this program might be prioritizing bandwidth to your online streams and reducing the bandwidth for League of Legends, causing you to disconnect.