WPSSO Core Pro and its WPSSO Schema JSON-LD Markup Pro add-on include a variety of additional product information in its Schema markup for WooCommerce products, including the product Brand, Color, Condition, EAN, GTIN-8, GTIN-12, GTIN-13, GTIN-14, ISBN, Material, MPN (aka Manufacturer Part Number), Size, and Gender.
WooCommerce itself already manages information on product Availability (aka Stock), Prices, SKU, etc., but other WooCommerce product attributes must be created to provide additional product information.
Google’s Testing Tool Reports a “Missing Product ID”?
If the Google Testing Tool reports a “Missing Product ID” error for your WooCommerce products, please note that the Product ID referred to by Google is not the Schema ‘productID’ property, but a general term used by Google for a missing globally common product identifier like the ‘mpn’ property (aka Manufacturer Part Number) or another globally common product identifier (ISBN, GTIN, etc.).
Unfortunately, the often used product ‘sku’ property (aka Stock Keeping Unit) is a number that changes from one retailer to another, so is not valid as a globally common product identifier.
If the Google Testing Tool reports a “Missing Product ID” error for your Schema Product markup (and assuming you are using the WPSSO Core Pro plugin and its WPSSO JSON Pro add-on), make sure you have created one or more WooCommerce attributes for the product MPN, ISBN, GTIN, etc., and update these values for all your products.