Managing personal Outlook.com account settings, security, and privacy
Hello,
Please try opening an InPrivate or Incognito browser window, then go to:
https://account.microsoft.com/security
Sign in and try changing your password from there using the "change password" option.
If you still get the same error, try using this link:
https://account.live.com/password/reset
If neither works, it could be a temporary service issue or security restriction.
Has this been happening for several days, or did it just start today?
Have you tried on a different device, or use different internet?