trp-ajax.php returns 500

A security plugin that you are using probably blocks our custom ajax (it helps to translate the strings that are loaded via JS).
You can use the following code to revert to WP admin ajax like this:

• Create an empty plugin like this: https://gist.github.com/sareiodata/76f701e01db6685829db
• Add the following code to the end of it:
  /* Revert to WP admin ajax instead of custom ajax url
*/
add_filter( 'trp_custom_ajax_url', 'trpc_use_wp_admin_ajax');
function trpc_use_wp_admin_ajax(){
return admin_url('admin-ajax.php');
}
• Install this plugin via FTP (copy it inside wp-content/plugins) or create a zip archive with it and install it via the WordPress plugin upload functionality