After your product starts to have reviews, you should be able to see the rich snippets display.
Rating stars displayed on Google Search Result
Right after the installation, the app submits the review and star rating to Google. Google will then crawl and display the star ratings snippet on SERP (Search Engine Result Page). That’s why our app can’t control when the snippet is enabled.
According to the update frequency of Google Robot (Usually it takes 1-7 days), comments will be displayed automatically.