The use of the admin-ajax.php file by our plugin is necessary for certain features to work. This includes loading more posts with the “Load More” button, image resizing, and adding comments in the lightbox (pro version). Here are some common reasons this isn’t working:
1) The error was due to complications when you first set up the plugin
If the feed is displaying and all features are working, there may have been a temporary disruption on your site that triggered the error to display. You can dismiss the error notice to remove it from the dashboard permanently.
3) A security plugin or a custom rewrite rule in your .htaccess file is blocking access
Many security plugins have a setting to workaround this issue. The use of admin-ajax.php is the officially supported method for using AJAX with WordPress so many themes and plugins do this.
4) The WordPress Address or Site Address settings are not correct
These settings are found on the Settings -> General page in your dashboard. Make sure the protocol (http/https) matches what your site is using.