The client may suddenly disappear after you log in. Usually, this is due to an authentication error or other miscommunication with your computer. To fix it, follow these steps:
Run the game as an administrator
- Right-click on your League of Legends shortcut
- Select Properties
- Check the box labeled “Run as Administrator” under the Compatibility tab
- Note: If you’re using Windows XP, you’ll need to log in as an Administrator instead
Sync your Windows clock
- Right-click on your computer's clock and choose "Adjust date/time"
- Select the Internet Time tab and click the "Change settings" button
- At this point you may receive a UAC prompt. After this prompt, click the "Update now" button to resync
Temporarily disable your firewall
If you’ve installed a third-party firewall, try disabling them before logging in. Windows comes with its own firewall, which you can disable by following these steps:
- Click on Start
- Click on Control Panel
- Click on System and Security
- Click on Windows Firewall
- Click on “Turn Windows Firewall on or off” (you may be prompted to enter the Admin password at this step)
- Under each network location, select the “Turn off Windows Firewall” option