Keep in mind that it may take some time for Google to read (crawl) your website and then display the stars accordingly.
The site query
Check if the stars can be displayed in the search results by doing a site query on Google.
To do this, enter the URL you want to check into the Google search bar in the following format: site:URL
- When you submit the site query and the stars are displayed, the search results may look like this:
Google's Testing Tool
- If the site query does not show any stars, you can use Google's Testing Tool to check if there are embedding-related conflicts. You can find detailed instructions on how to do this here: How do I determine whether the Google Stars are correctly integrated on the website?