According to Bloomberg's sources, the issue presented itself when Nintendo noticed that certain third-party sellers on Amazon were undercutting official products. They would essentially purchase the products in Southeast Asia, where they were presumably cheaper, and then sell them in the United States via Amazon.In an attempt to reassure Nintendo, Amazon offered to attach labels to products to guarantee their authenticity. However, the proposal wasn't deemed enough of an assurance to Nintendo, and the Japanese company ultimately decided to remove its products from Amazon in the US.