Error Updating Password: Unknown Validation Code
Last week, Wizards of the Coast had sent an email to accounts on the legacy database about a security breach and advising affected people to reset their passwords. Doing so has not been a simple endeavor however. Players are receiving an error message “Error updating password: UKNOWN VALIDATION CODE” when attempting to reset the password.
A workaround user ManilaBeans from the official MTG Arena Forums used was changing the email address of the old Wizards account.
I HAVE SUCCESSFULLY FIXED MY ACCOUNT. The problem seems to have been caused by the fact that I had the same email address linked to my two wizards accounts:
1. Old Wizards account (the one linked to my DCI number)
2. Arena account
In a previous attempt to fix the issue I have reset the password to my old wizards account (DCI account) and changed the associated email address to a different one. This initially did not solve the issue. I have since gone back and requested another password reset on the old account (triggering an email to be sent to the new email address associated to it). After the password reset on the old account I then triggered a forgot password on the Arena account and VIOLA! I got the password reset email right away.
I have now been able to reset the password on the Arena account and am now able to log into it again.
Source: MTG Arena Forums
Here are the latest update from Wizards, and the steps you need to follow if you want to reset your password.
For players who are required to reset their account password, we are continuing to investigate why some players are not receiving their password reset email.
For players who have not received their password reset email, you can manually request an email by going to: https://myaccounts.wizards.com/forgot and entering the email address associated with your MTG Arena account.
If you do not receive the email or you no longer have access to that email account, at this time you will need to contact support for further assistance: https://mtgarena-support.wizards.com/hc/en-us/requests/new?ticket_form_id=360000022266
We apologize for the inconvenience, and thank you for your understanding as we continue to investigate the issue.
Source: NOV 22 – Account Password Reset