You can only add the @icloud.com address that is already on file in your account. How do I fix this?
I have a third party email that the internet provider is discontinuing so I need a new email. I created a new iCloud email account and I have verified that it works. Then I tried to change the AppleID to the new iCloud account and I get the "You can only add the @icloud.com address that is already on file in your account.". How do I add the @iCloud.com address so that I can use it?
MacBook Pro 16″, macOS 10.15