By any chance is your root email address similar to the one you use for your regular Amazon life (kindle / shopping / prime) etc? You should be able to log in using that root account using your usual Amazon email and then proceed to reach out to support.
As root you could also assign the IAM roles to individual users for specific buckets.
This is most likely what is happening is the shopping website and AWS are now trying to make you create at least 2 accounts and the captchas will start showing after that
As root you could also assign the IAM roles to individual users for specific buckets.