Google rich snippet is not working & not Consistent

I have been using KK Star Rating plugins for years and it used to work perfectly. but of late the rich snippet feature is not working perfectly or not consistent.

Sometimes when we publish the article the rich snippet works and then disappears after a few days and sometimes it doesn’t appear at all.

Here are two examples

1. For this article, the rich snippet never worked

https://www.begindot.com/best-education-wordpress-themes/

2. For this article, the snippet was working but disappeared suddenly.

https://www.begindot.com/best-buddypress-themes/

So, can we have a look if there is an issue with the markup as we are doing the same thing for all article and it is working perfectly for some?

The page I need help with: [log in to see the link]