Validation Result: Products Missing GTIN and MPN
Products to be advertised in Google Shopping must have either a Global Trade Identification Number (GTIN) or a Manufacturer Part Number (MPN). If neither a GTIN or an MPN is supplied, your product will not be eligible for Google Shopping ads.
GTINs are a globally unique identifier and are usually registered by the manufacturer. GTINs come in several forms, including 8-, 12-, 13- and 14-digit numbers.
MPNs are assigned by the product manufacturer, but may not be globally unique. GTINs should be used in preference to MPNs wherever they are available.
Shopify stores GTINs in the Barcode field for each variant of a product.