Manually link your Etsy products with Shopify products
1.) If your products not contains the same sku and variations options then you need to link manually those Etsy products with Shopify products. FROM HERE.
Products are not available in the App "Import products from Shopify to App
1.) For linking of Etsy listings with Shopify products then the products must be present in the App If not import FROM HERE.
If products are available only on your Etsy store
1.) In case your Etsy products are only available on Etsy then for proper linking products must be present on Shopify and App. Create Etsy products on Shopify FROM HERE.