Structured Data Not Supported for Unpaid Listings in Google Shopping Tab

Instead of using Structured Data for generating product result (like what happens with Search, Images, etc ), the free listings in Google Shopping tab listings do not add you products based on Structured Data implementation.

You must submit a feed through Google Merchant Center and meet the additional eligibility requirements for enhanced listings to appear in these results. This was recently added in Google’s support documentation for the data and eligibility requirements for Surfaces Across Google.