Managing personal Outlook.com account settings, security, and privacy
Hey there! Nice to meet you!
Based on the error message you received and since you haven't signed in to your account for several years, I'm afraid 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
Also, since you mentioned that this is an Outlook account, please be advised that email addresses with Microsoft domains, such as Outlook, Hotmail, Live, or MSN, cannot be associated with any Microsoft account again once they have been removed or deleted. This is stated in the following article, particularly under the "Remove an email address" section:
https://support.microsoft.com/Outlook/add-or-remove-an-email-alias-in-outlook-com
Thank you for your understanding.
Best regards,
Darhyl