Managing personal Outlook.com account settings, security, and privacy
Hello RigelCastelo
Thank you for using Microsoft products and posting them to the community.
I understand that you want to restore the alias of your account, and I understand that your pain and difficulty is not something we want to see.
But we regret to inform you that If you remove the original alias, it's a Microsoft domain account. For example, @hotmail.com, @live.com, @outlook.com, or @msn.com, once deleted, can't be reassociated with a Microsoft account. For more information, see this link: Add or remove an email alias in Outlook.com - Microsoft Support
The reason why you are seeing a message that the account does not exist is because the deleted Microsoft domain alias can no longer be bound to the new account.
If possible, please also contact the associated account to find out how to change the associated information if you are unable to send or receive emails, so as to avoid further loss to you.
We hope you find this information useful. Please let me know if you have any questions or if there is any progress on this issue.
Best wishes
Forry.F - MSFT | Microsoft Community Support Specialist