There can be two situations
Your Rich Snippets were visible earlier, but not now;
Rich Snippets were recently added to your Magento 2 store, but still not visible.
In the first situation, you should test and validate rich snippets markup with the help of Google’s rich snippets testing tool on a few webpages. If you find the markup to be invalid, you should fix it and then submit the page to indexation using Google Search Console. After submitting the page, Google should update that page in its SERPs in a matter of minutes.
In the second situation, Google might not have re-indexed these pages yet. You can submit a few different pages to indexation using Google Search Console and then test the results in SERP.