Unable to Log In to OCI Account and Not Receiving Password Reset Email

Summary:
I cannot access my existing OCI tenancy because the sign-in fails, and password reset emails are not being delivered.

Content:
Hello,

I cannot sign in to my existing Oracle Cloud Infrastructure tenancy.

Identity Domain: Default
OCI Region: Chuncheon, South Korea
Original administrator email: w********@hanmail.net

The OCI login page says that the credentials do not match Oracle's records.

I requested a password reset several times, but I did not receive any password reset email. I checked the inbox, spam, junk, trash, and blocked sender settings.

Other Oracle Cloud notification emails were previously delivered to the same email address.