Personal Microsoft account cannot access MFA setup after primary alias change – “username might be incorrect” error

Question

Hello, I am experiencing a technical issue with my personal Microsoft account (Outlook.com) after removing my old alias and switching to a new primary alias.

I recently deleted my old alias ******@live.de due to a confirmed security exposure. The alias appeared in a public credential leak, and shortly afterwards I observed multiple unauthorized sign‑in attempts from different geographic regions. Passwordless authentication and MFA blocked these attempts, but because the alias was compromised, I removed it and switched to a new primary alias (masked for privacy, ends with @outlook.de) to secure the account.

Since the alias change, MFA setup cannot load correctly.

Error: When accessing https://aka.ms/mfasetup and entering my new primary alias, the system returns:

“This username might be incorrect. Make sure you typed it correctly. Otherwise, contact your administrator.”

This is a personal Microsoft account, so there is no administrator.

Additional technical symptoms:

• When opening https://aka.ms/mysecurityinfo, after selecting an sign in options, the system recognizes my account and prompts me for my PIN.
• After entering the PIN, I am receiving “An error occurred during sign‑in using the primary key credential. Please try again.”

The behavior suggests that the MFA registration object is still bound to the deleted alias and is now in an orphaned state.

What has already been verified:

Primary alias change is correctly reflected on account.microsoft.com.

Passwordless sign‑in works normally with the new alias.

Old alias is fully removed from the account.

Authenticator reinstallation does not resolve the issue.

Account activity logs show normal behavior except for the earlier unauthorized attempts.

Technical assumption: The MFA registration object in the backend still references the deleted alias. After the alias removal, the identity no longer resolves correctly in the MFA endpoint, causing aka.ms/mfasetup and mysecurityinfo to fail with the “username might be incorrect” message after PIN verification. As a result, MFA cannot be loaded, reset, or re‑registered through the standard self‑service flows.

Question: How can the MFA registration object for a personal Microsoft account be reset when the old alias has been deleted and MFA setup returns “username might be incorrect”?

Is there a process for Microsoft support to manually remove the orphaned MFA object or re‑synchronize the identity so that MFA setup can function again under the new primary alias?

Thank you for trying to help me

Alen