The following refers to Amazon feeds and merchants who do not have UPCs and have Brand Registry to use "Part Number" as the key attribute:
Map Style Number to all Simple products (sellable; not parents of variations). If a simple SKU product does not have a style number and it is submitted under a registered brand name, then that product will not go live until it is submitted with a style number.
If a merchant uses a parent SKU as a selling SKU before using GoDataFeed
Also, if an SKU is successfully listed with quantity and price, but it's supposed to be a parent SKU (this happens if merchants list products manually using their own parent SKUs to sell products prior to coming to GDF), then Amazon cannot change the selling SKU to be a parent SKU. Amazon says to delete the parent SKU then resend it with the correct mapping.
Duplicate Style number
If ever we send more than one SKU with the same style number, whether because we didn't realize the merchant had duplicate 'MPN's at one point or the platform data needed to be modified by custom rules to create unique numbers, then the skus will end up on the same ASIN. You must delete them for 24 hours and then correct the duplicate and send them again.