There are specific requirements before one can start Google Shopping.

The below requirements need to be approved for Google Merchant Center - 

1. An online store with a unique domain - A domain can only have a single merchant center associated; this means you cannot use myshopify.com URL for Google Shopping.
2. An active terms of service page.
3. An active refund policy page.
4. A store that is accessible publically (no password).
5. A valid payment provider - will ensure every customer can check out after coming to your site.
6. Maintain an easily accessible page containing contact information on your website.
7. Sales tax & Shipping rates depend on the country of sale.