If Amazon returns the following error when you are attempting to list, here is how you clear it.
||Description and Solutions
|The SKU data provided conflicts with the Amazon catalog. The item_id value(s) provided correspond to the ASIN XXXXXXXXXX, but some information contradicts with the Amazon catalog. The following are the attribute value(s) that are conflicting: XX. If your product is this ASIN, then modify your data to reflect the Amazon catalog values. Else, check your value(s) for item_id are correct.||
Amazon generally returns this error when you are attempting to create a new listing. The error indicates that the UPC or EAN you provided already exists in Amazon's catalog—meaning your product has already been listed. Amazon also provides the ASIN for the listing your UPC or EAN is associated with.
If the ASIN Amazon provided doesn't correspond to the item you are trying to list, check that you entered the correct UPC or EAN. If not, update the UPC or EAN. If they are correct, notify Amazon that someone has misused the UPC or EAN and that you want to list the item properly.