Creating new ASIN on Amazon
When you as a seller send your product to Amazon and the GTIN barcode (UPC/EAN) you've assigned to your product has never been registered on Amazon by any other seller, well then well done!
Amazon will create a new ASIN (aka listing) on their marketplace for you and use the data coming from your storefront to do so (such as title, brand, variation attributes, etc).
Matching to existing ASIN on Amazon
In case you give Amazon a GTIN barcode (UPC/EAN) that has already been in their catalog, well then be aware that there's an ASIN/listing created with that barcode on Amazon already and you will be forced to match to that existing ASIN/listing as well as the product data used to get the listing created originally.
Matching Error
If you used Shoppingfeed to send products from your storefront to Amazon and some of them matched to existing ASINs and some of the product data does not correspond with what Amazon has in their catalog - then Amazon would reject those products with error code 8541.
Ways to fix the Matching Error:
1. Follow Amazon requirements
There's no need to actually go and manually change the data in your storefront since we have the Matching Tab in Shoppingfeed that allows you to fix matching error 8541 easily.
In the ASIN Matching tab, you can see all the SKUs with the pieces of product data that do not match with what Amazon already has on their end for a given ASIN. Next to each product, you're going to see the name of the field in error, also the value you sent to Amazon, and the value that Amazon requires to match a given ASIN.
Simply choose "Yes, send the correct value" and we will send the value required by Amazon without the need to make changes to your product data in your storefront or via rules.
Alternatively, you can change the value for the attribute in question directly in your storefront.
2. Matching to a different ASIN or creating a new ASIN from scratch
If you believe that the value that Amazon requires is wrong and you do not want to match it - you would need to provide Amazon with a different GTIN barcode (UPC/EAN) for this product to either match to a different ASIN or create the new ASIN from scratch.
You can also try reaching out to Amazon Seller Central Support directly with a request to update product data on a given ASIN but be ready that such requests typically require some time and effort.