One or more of the CNAMEs you provided are already associated with a different resource

Hello.

If the CNAME record is already in use by another AWS account and you do not own the AWS account, you will need to contact AWS Support.
You can contact us for free by opening a case under "Account and billing".
However, there is a possibility that the free support will not be able to help you with this issue, so please try contacting them via "Account and billing" and if they do not seem to be able to help you, please consider using paid support.
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html

https://repost.aws/knowledge-center/resolve-cnamealreadyexists-error

If you don't have access to the account that contains the source distribution or you can't deactivate the source distribution, then contact AWS Support.

AWS Support can be accessed from the following URL:
https://console.aws.amazon.com/support

Contacting with "Account and billing" doesn't solve the problem.

That means the need to pay 30$ on AWS Support to solve the AWS bug and be able to use the domain.

AWS is a great deal.