Teenkerbelle,
Since this an issue with a specific game, World of Warcraft, you need to post in WoW’s forums for the right teams/people to see it.
That said, that error message means that the game version on the server and on your game client do not match. Meaning, you need to install the update so that they do match.
If the launcher isn’t detecting an update, completely log out of it and close the launcher app. Make sure the Agent process sucessfully closes in your Task Manager. Then reopen and relog.
If that doesn’t work, follow the same steps, but additionally restart your system after closing the launcher.