Hello,
WPSSO Schema JSON-LD Markup plugin generates the error on the single product page http://prntscr.com/pq7wd9 If the plugin is disabled you have only 3 warnings http://prntscr.com/pq7ww8 So, keep plugin disabled and start the new check.
What those warnings mean:
– your product does not have reviews and ratings http://prntscr.com/pq7xfn Once users leave the reviews and rating these 2 warnings for the product will disappear. Our theme is not responsible for how your users add the reviews/ratings.
– “This Product is missing a global identifier (e.g. ISBN, mpn or gtin8)” – WooCommerce does not have option to add the ISBN, mpn or gtin8, so if your products have this information and you want to add it look for an additional plugin if not then just ignore this warning.
In general, the theme is not responsible for schema for the products, it’s WooCommerce plugin area.
Regards