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

Resources for Warlock class quest in World of Warcraft: Classic.

Information about quest resources.

Information about the character clone service in WoW Classic and Burning Crusade Classic

What to do if you redeemed a WoW Token for game time and you didn't receive the game time

Information about the World of Warcraft behavioral warning

Information about the Collections tab feature in WoW Classic Era

How to move a World of Warcraft account to a new Battle.net account.

How to launch multiple WoW clients on the same computer

How to make scrolling combat/healing text smaller of bigger in size.