Description:

This error is the result of the expiration of some security certificates due to the age of your operating system.

Error code:

First solution:

• Make sure that you are using the correct EMAIL and password, not username and password

Second solution

• Launch the Firestorm launcher
  
• Choose your expansion and go to your full client folder and select it.
  
• Select "Settings" and click on "Analyze and repair"
  
• Wait for the repair to be completed
  
• Try to log in by clicking on the "Play" button

Third solution:

• Close your game
• Delete the following  folders: Cache and WTF
• Launch your game

Fourth solution :

Open a CMD by pressing simultaneously Windows+R, then write "cmd.exe" et click on "OK".
In the window that opened, enter the following command: ipconfig /flushdns. Press enter.
Try to relog into the game.

Fifth solution :

Add World of Warcraft as an exception to your anti-virus (Windows Defender is the default one. If you have another one we recommend you do uninstall it. Windows Defender is a good anti-virus and having another one may create conflicts with it).
Here is how to do it :

• Write "Security" in the Windows search bar and click on "Windows Security".
• Go to "Virus & threat protection".
• Go to "Manage settings" under "Virus & threat protection settings".
• Scroll down to "Exclusions" et click on "Add or remove exclusions".
• Click on "+ Add an exclusion", then "Folder" and select your game folder.

Once done, try to relog again.

Sixth solution :

Install the launcher and open it.
Go to Shadowlands and click on "Install", a window will open asking you to select a place where it will be installed. Select your actual game folder and click on "Yes" on the question "Does the selected folder contain a complete game?".

The launcher will update your game, once done you can launch it and try to log in.