In an effort to bring exciting features on Google Product Search, and to make sure your product offers are included product pages. Google announced that “starting in late August, product offers in Electronics, Books, and Media categories from US merchants mayn’t appear in Product Search if your data feed doesn’t include necessary unique product identifiers, such as “MPN, Brand, GTIN/UPC/EAN or ISBN”,” stated Google. We’ll make similar changes to Product Search in the UK and Germany at a later date.
Google advises, “to avoid seeing a drop in traffic from Product Search, we urge you to start including these unique identifiers as soon as possible, for as many categories as you can get this data.” You can find unique product identifier information on Product Search product pages, under “technical specifications” section for Electronics items, “Tracks” or “Details” section for Media, and “Overview” section for books.
More Info: Help Center