The ASIN or UPC is invalid. Access to Products.GetMatchingProductForId is denied – AccessDenied
This error occurs when our systems (SellerChamp back end processes) get an unauthorized 401 error when calling Amazon API using your Amazon MWS token.
Amazon offers two selling plans:
Professional Selling Plan
In order to allow SellerChamp access and ability to manage your Amazon Seller Central, you're required to have the Amazon Professional Seller Account.
If you've just recently acquired access to your Amazon Professional Account, please give it about 24 - 48 hours will Amazon gets your account thoroughly setup.
If you still face any trouble, please get back to us and we'll investigate further.