If you receive the message „Your AccessKey Id is not registered for Product Advertising API.“ in reply to a request to the API, this means that your account is not activated for the country to which the request was made.
Your account for the Amazon API is not automatically activated for all countries the API supports. Typically only for the country in which the account was created.
To activate your account for other countries, you have to register it via the PartnerNet site of the respective country. If this does not work, please contact the Amazon PartnerNet Support.
Amazon PartnerNet Homepages