VENTCOUVERT VDP SAS review for Google & YouTube

Our products are approved and synced in merchant center through content API, but not showing up in Google Shopping. Google allows free listing, and this app promise us the same, so I do not understand how can we show our products in Google shopping from our Shopify store... We also get warnings of color, size, gender (etc...), whereas we have lots of variants. I read on the Shopify website that it is not necessary to add these in case of having variants, but still we get the error in the google channel and in merchant center... I'm looking forward to hear from the support team, to help me resolve this issue.