This is Amazon’s answer:
Amazon.co.uk, Amazon.fr, Amazon.de and Amazon.co.jp each has a unique Author Central website to set up an account, even if you’ve already joined Author Central on Amazon.com. Not all the features in Amazon.com’s Author Central will be available in Author Central on the international sites, though we look forward to adding all of them in the future.
To get started, visit Amazon.co.uk Author Central (https://authorcentral.amazon.
While your existing Amazon.com/uk/de/fr e-mail address and password will be accepted on our American and European sites, the same is not true for Amazon.co.jp. You’ll need to set up a new account in order to order from Amazon.co.jp.