Trying to add a product, bought GS1 barcode… now what?

Not sure if it matters, but this product has variations.

I’ve purchased UPCs on GS1, but when I put one in the “External Product ID” field, it still says “The SKU does not match any ASIN and contains invalid value(s) for attributes required for creation of a new ASIN.”

I was under the impression that this was what I needed for External Product ID… do i need to register it or something??