Cannot change apple id to the icloud email address
Recently, I created an icloud email address, and wanted to change the apple id to match the new icloud email address. When trying to do so I am prompted with a message " This email address cannot be used as an Apple ID at this time." When searching online people suggested to remove the icloud email address from the contactable section in icloud settings. However, I am not allowed to that also as I am prompted with another message "Your email address cannot be removed. Go to iMessage and Facetime Settings." Heading to the iMessage and Facetime Settings, I untick/de-select the icloud email and address. Then I go back to remove the icloud email address from the contactable section in the icloud but with no luck and I am prompted with the same earlier message, "Your email address cannot be removed. Go to iMessage and Facetime Settings."
Could you help with this issue? What I want is to change my apple id to match the newly created icloud email address.
iPhone 11, iOS 14