iCloud custom domain

Hi there! I have a problem with iCloud custom domains over cloudflare.
Everything was working fine. I inveted a second Apple ID (also mine) to my Apple family and transferf a custom mailadress to one Apple ID to another. All fine. I then deleted the mail from the secon Apple ID to get it back to my old Apple ID and then deleted the old Apple ID. But now I can‘t get the custom adress back to my ild account. It says „this adress is allreday connected to a different Apple ID“. I can‘t quit the delteting of the new Apple ID to get back to the mails and I can‘t find a setting in Cloudflare to disconnect or delte mailadresse to reset it.
So, please help me! I can‘t get Mails fron the address. Tried forwarding it over Cloudflare wich is also not working. Is ther anything I can do? Apple told me to wait 30 days until the second Apple ID is deleted fully to get back to the custom mailadress.

Hope you understand my problem. I am a total newbee on that stuff. Thanks! Thomas