SKU is associated to more than 1 GCID
SKU [card-game-7] is associated to more than 1 GCID, which is not allowed. Please send a delete feed for this SKU and all other SKUs with the same attribute values [merchant_suggested_asin], and then resubmit the SKUs
This error might appear when the product you want to link to Amazon, has already been added to your Amazon Seller account but with a different SKU. To fix this error, please make sure to adjust SKUs, so that they are the same on Shopify and Amazon.