Hello, thanks for reaching out.
To clarify, are you using a personal Microsoft 365 subscription or a business account managed through the Microsoft 365 admin center? This detail matters because Microsoft doesn’t allow two accounts to share the same email.
If it’s a business account, sign in to the admin center, go to Users, then Active users, and edit the user’s email to add the correct one as an alias.
If it’s a personal account, go to account.microsoft.com, add your correct email as an alias, verify it, then make it your primary email. You may need to delete or rename the second account first if the address is already in use.