Google’s Structured Data Testing Tool and/or Google’s Search Console for site owners may report the following errors for the default Schema JSON-LD markup offered by WooCommerce:
WooCommerce manages information on product Availability (aka Stock), Prices, SKU, etc., but additional WooCommerce product attributes must be created to provide more product information for Google.
The WPSSO Core Pro plugin (and its WPSSO Schema JSON-LD Markup Pro add-on), for example, include a variety of WooCommerce product attribute values in its Schema markup, 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.
WPSSO Core Pro and the WPSSO JSON Pro add-on provide complete Schema markup (aka Google’s Product Rich Card) for WooCommerce products, including all variations and extensive product information (size, weight, sale prices / dates, color, condition, etc.) – far beyond the basic Schema markup provided by the WooCommerce plugin itself.
WPSSO Core Pro can also read several custom WooCommerce product attributes, if / when you create them in your WooCommerce store: