Change Primary Apple ID to an Existing Alias
I have an old gmail email account as my primary Apple ID. I have an additional iCloud email account set as an alias. If I have reason to believe the old gmail account is no longer secure or I simply don't use it anymore, is there not a way to make the iCloud email my Apple ID? When I go to change my Apple ID and enter the iCloud address and click continue, the loading icon displays and the screen just hangs indefinitely. Nothing changes. It seems like there should be a way to change this if I no longer use the Apple ID email address. Do I have to delete my iCloud email address (is that even possible?) or create another new iCloud email?
iPhone 7, iOS 10.2