"The server was unable to authenticate your gameplay privileges. Please contact Customer Support to provide them with your registered e-mail address. For additional support, please visit http://support.guildwars2.com."
What is an Error 21?
Error 21 is a fairly rare error code that pops up when the game is unable to find a game account associated with your login information. This is often the case when trying to access Guild Wars with your Guild Wars 2 account or vice versa, and will often prevent you from accessing the game.
How do I fix an Error 21?
Here's a few troubleshooting steps you can take before contacting support:
Locate your local.dat file—which by default is stored in your Documents> Guild Wars 2 folder—and delete it.
Next find your Gw2.tmp file—typically found in your C:\Program Files (x86)\Guild Wars 2 folder—and delete it as well.
After both files have been deleted, launch Guild Wars 2, download any updates, and login to see if the problem persists.
If you are still encountering the error, please submit a technical support help request
Like other Error Codes, there are often variants of the Error 21 code that will pop up depending on your circumstance. We ask that you submit the full code to support when submitting a ticket: