You probably get this error : “You are using UPCs, EANs, ISBNs, ASINs, or JAN codes that do not match the products you are trying to list.”
This error typically happens on Amazon if you’re listing a Brand that already has UPCs and Amazon is restricting the Brand from adding more UPCs (to prevent duplicate listings). The issue typically isn’t with the UPCs themselves, but with the restrictions placed on the Brand. To test if this is a Brand restriction, change the “Brand” field to something else unique and it should solve the issue. If the issue goes away, we know it was a Brand restriction.
Example: Let’s assume you're listing a Nike shoe but trying to use your own barcode, this will not work since your barcode is different then Nike's own Amazon brand registered barcode numbers.
The solution or "work-around" to this is to not input the brand's name (ex: Nike) in the brand field, but instead input your DBA or Amazon company or store name in the brand field instead and then input the brand's name (ex: Nike) in the item description. The moment you type "Nike" into the brand field amazon's automated system cross references Nike's own barcode numbers against the one's you're trying to enter.