Using Classic Outlook on Windows for personal email, calendar, and contact management
Thank you for the information.
Kindly double-check if the account name was typed correctly. Also, if you have not signed in for more than 2 years, your account may have already been deleted/closed due to inactivity.
As stated by Microsoft, accounts that have not been signed in or have been locked for more than 2 years will be deleted due to inactivity, and they can no longer be recovered: https://support.microsoft.com/topic/microsoft-account-activity-policy-7c0a9fa7-0982-b7c6-fd72-df852b63699f
If none of the scenarios above are applicable, the error you are experiencing is an indication that your account was compromised. The hacker was able to remove the account's primary email address/security info and replace it with their own email address, which is why your account is not recognized.
The only way to recover a hacked account is through the official Microsoft troubleshooter guide:
If the account recovery web form doesn't work, and since the security info has been replaced by the hacker, I'm afraid there is no other working method to recover the Microsoft account, and Microsoft Support cannot help either.
Thank you for your understanding! Please feel free to let me know if you need anything else.
Best Regards,
Darhyl