Error Code 8566
This error means that a SKU in your Amazon feed doesn't match any ASIN in Amazon's catalog and that the product data you have provided is not sufficient for ASIN creation.
Make sure that you create the required Amazon fields correctly to connect ASIN. All required fields must be completed. You need to match your products to the relevant existing listing. Your product feed needs to contain unique, standard product identifiers (ISBN, UPC, EAN, etc.) for every product included. If you’re creating a new product on Amazon, you’ll use the same ID product information. It’s also important to include the manufacturer part number, brand, and product dimensions(weight, length etc.). This information will also make it easier for Amazon to create a new ASIN for the new product.