Google has tightened the rules regarding the layout of the reviews
Now before you add the markup you need to make sure that the reviews do not contain swear words and obscene expressions. Otherwise Google will not show extended snippets of this type for this site. To avoid losing the snippets, you need to remove the invalid reviews or to remove the markings.
Recall that in August of this year, Google turned the local search results block reviews from critics. In September, the search engine added to the panel's knowledge the new block "Feedback from Internet". It includes the content generated by users.