Miss attributes during load

Hi, congrats for your plugin it helps a lot of people thanks!

I have a problem loading my product-feed because, after checking the XML, google answer that are missing the (‘gtin’ [gtin], ‘marca’ [brand], ‘mpn’ [mpn])… where i can put this values? Are they from woo commerce or in your plugin?

thanks
Angelo

https://www.ads-software.com/plugins/woocommerce-google-merchant-center-feed/