This works for me https://business.czar to.com/2019/12/11/update-your-shopify-facebook-product-feed-with-missing-attributes/

I used this technique  as per above "Fix missing fields on facebook's Shopify feed" ; but it a pain to update each and everytime you add a product. Is there any other work around? 

is this resolved yet? Whom do we need to contact to raise a ticket? This is frustrating to see this when there are apps who can do this, then why not shopify?