Managing personal Outlook.com account settings, security, and privacy
Hi, I'm John! I will help you with this.
To help narrow down the issue:
- When was the last time you were able to sign in to the old account?
- Did you close the old account or remove it as an alias from another Microsoft account?
- Are you seeing the message “That Microsoft account doesn’t exist” on the Microsoft sign-in page?
Also, please try searching for the account using these steps from Microsoft: https://support.microsoft.com/account-billing/forgotten-your-microsoft-account-username-b2049472-3b8f-27d3-61c6-67a668453f4c Click on "Search" and follow the instructions provided.
If you receive any error messages, such as “account doesn’t exist” or anything else, please let me know.