Nerdimports review for Google & YouTube

This app is not working. I've had it installed for months and although it says 250+ products are listed, none of them show up in the Google shopping tab. When I go into the edit page on Shopify for my products, it's difficult to actually fix many of the problems that Google apparently has with my listings. But even if I add size, category, GTINs, etc. The listings are still no where to be seen.