You are attempting to change an identity attribute for this SKU
You are attempting to change an identity attribute for this SKU. To proceed, please delete this SKU and recreate the SKU with the appropriate identity attribute. For more information and detailed instructions, see: http://sellercentral.amazon.com/gp/help/23191
This type of error might appear for various reasons. The most common causes are duplicated SKUs or duplicated barcodes for one or more products. If this is the case, Amazon cannot process the request and generates this error. Most likely it happens for the products with variations.
To resolve this error, please make sure that SKUs and barcodes are unique for your Shopify products.