League of Legends unexpected error with the login session

On screen: There was an unexpected error with the login session. Please try again.

What it actually means

Session state lives in the Riot Client, not in the League client. When a RiotClientServices.exe process is left hanging after a crash, a forced close or a patch, it holds a dead session handle. The League client then asks it for a token and gets the dead one back.

That is why Riot's own fix consists entirely of killing processes rather than anything network-related.

How to tell which one you have

If killing the processes and signing in again has ever worked for you, it was local. If it survives a clean reboot and the Riot status page shows login or platform problems, or everyone in your region hit it at once right after a patch, it is Riot's side.

Fixes, in the order worth trying

1. Alt+F4 and choose sign out, not exit — This is Riot's own sequence and the distinction matters — exit leaves the session handle in place.
2. End every Riot process in Task Manager — RiotClientServices.exe, LeagueofLegends.exe and RiotClientUx.exe.
3. Relaunch as administrator — Then sign in again.
4. If it returns every launch, rename the Riot Client data folder — C:\\Users\\<you>\\AppData\\Local\\Riot Games\\Riot Client\\Data. It rebuilds on next start and forces a fresh session.
5. Close Killer Control Center — Riot names this explicitly. KillerServiceNetwork.exe on MSI and Alienware laptops interferes with the client's local connections.
6. Change DNS or turn off a VPN — The regional variant, where the client resolves the wrong authentication endpoint.
7. If the client language reset itself, run a repair — That symptom points at a damaged installation rather than a session problem.

Operator documentation: support.riotgames.com. Riot's page is current, last updated 31 May 2026. Note that the old support-leagueoflegends.riotgames.com and support-valorant.riotgames.com domains now redirect into support.riotgames.com/en-us/<game>/, so older links you find elsewhere are stale.

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