Error 0U: League is having trouble talking to its servers
League clientServer sideThe message
We're having trouble talking to some League servers. If this problem persists, please reach out to Player Support with error code: 0U.What it means
The League client can't reach part of Riot's backend, so you can't get into a lobby. Riot Support has called it out by name during outages in 2020 and 2024.
What to try first
Look at League server status. If it's clear, exit the Riot Client from the system tray and log in again.
Is it you or Riot? If lots of players are hitting this at once, it's probably the servers. Check League server status before you start reinstalling things.
What Riot has said about 0U
You'll find 0U on the tooltip of a grey Play button, worded the way it's quoted above. So the client already admits it's a server problem. Its only advice is to contact Player Support if it keeps happening.
Riot's support team has named the code twice. On October 20, 2020, its main account said North American players were hitting intermittent login trouble across Riot's games, and that League players couldn't get into a lobby because of Error 0U. On November 13, 2024, the Spanish support account listed 0U next to 9S and 6U while League and TFT were struggling. Riot didn't give a cause either time. It said it knew and was looking into it.
How to get past it
Check League server status before anything else. When 0U is part of an incident it goes away once Riot fixes its side. Nothing on your PC brings that forward.
No incident listed? Exit the Riot Client completely from the system tray (closing the window leaves it running) and sign back in. Granted, that's advice you'll find on plenty of pages here, but it's also what fixed 0U for the one player who reported a fix. If the button is still grey after that, do what the message says and open a ticket with Riot Player Support, quoting 0U.
The same grey-button symptom comes with Error 9S 6U.
What players found
Reports of 0U arrive in bursts. In November 2024 a thread filled up fast with players who had the same grey button, and one of them got back in just by restarting the client. In October 2020 it somehow hit a cluster of players around Denver on the live client, and nobody ever learned why that city. It came back up the same day. One player there had already uninstalled the game and reset the router before it came back on its own (neither made any difference).
Player reports paraphrased from various Reddit threads, read October 2, 2026.
Other wordings of the same error
Error 0UError code 0UError code OULoL error 0ULeague error code 0U
Related errors
Sources: Riot Games Support on X, October 20, 2020, and Riot Games Support Spain on X, November 13, 2024; player reports paraphrased from Reddit. Riot has no support article for this code. Checked October 2, 2026.