Hello Sergey, can you give us some general informations how to solve the problem. I think many users of this plugin has the same problem. There must be general reasons for it.

As I said before, there is no any common solution. Any error on site may lead to the issue. That is why I need access to site to check the issue or the error message from Ajax Response. 

Creative Fertile,

Could you send me your site url, I will test the issue on your site, suggest you a solution and post it on the thread.

Sergey, thanks for replying! I used Chrome debug to take a look. Screenshot is attached. If you need more, let me know.

Hello! This somehow resolved itself a little while ago (I uninstalled and re-installed the plugin along with a lot of other site changes). But it appears to be back. Did my above screenshot help? I can send more information if needed.

Here is another screenshot if it helps, see attached.