You need to update your Shopify theme to keep your site secure and ensure that you'll get access to all of the latest bug fixes and updates to the code. But after updating the theme, there may be some errors such as losing reviews.
Please refer to the tutorial below to take reviews back after changing or updating the Shopify theme in your store.
Step 1: Go to your Ryviu dashboard > Settings > General, click the Add snippet codes button under the Connections section.
By default, Ryviu will add its snippet codes to your Template/product.liquid and Sections/product-template.liquid.
Step 2: Add stars rating under the product title in your collection page by following this instruction: Stars rating for collection page
If you use Online store 2.0 themes, please follow our instruction to add reviews section and star ratings for your product page.
Please feel free to contact us via live chat if you got any queries :)