I had an issue with the rating stars not displaying on reviews or form. (when logged into wp-admin the stars displayed ok- log out..gone)
I discovered when the page rendered the css was looking for the newstars.png in this location:
http://fonts.googleapis.com//newstars.png
this may be because of W3TC caching not sure
Here’s what fixed it edit the plugin css file:
wp-customer-reviews.css
replace newstars.png with absolute address:
http://www.example.com/wp-content/plugins/wp-customer-reviews/newstars.png
Hope this helps someone and maybe a fix can be incorporated in future release
https://wordpress.org/plugins/wp-customer-reviews/