For the new theme, please make sure our applications rich snippet information is connected to your product page. You can provide us the link to your store and we will do the test for you.
Then, please re-crawl your site with Google and after they complete the re-crawl the reviews should show up in Google search results again. For more information on how to do that you can see here: https://support.google.com/webmasters/answer/6065812?hl=en
Let me know if I can help with anything else. Thank you!
Quynh Nguyen
After I changed the theme, the product reviews are not showing on google. Can you tell me why please?