The client you are using to log in to the game is out of date or there is a mismatch between the client and server versions

Error: An updated version of World of Warcraft is available.

Changed my language on the menu but does not apply Want a different language on the game then the Steam Client.

Restoration requests for dead Hardcore heroes in D3/RoS.

The version of the game you are attempting to play does not match our current game servers.

What to do if there is a Game Version Error when launching Warcraft Rumble

Information about private server services and how to report them

How to launch multiple WoW clients on the same computer

Group invite errors with "This friend is playing a different version of world of warcraft"

This occurs because your game client does not match the version on our servers.