What? THis is a XStore theme CORE issue, this has nothing to do with plugin or a 3rd party – in this care; the core plugins from you are the 3rd party that causes issues.
When i disable the XStore theme CORE from you the plugin works, when i enable it, it doesn’t work cause of the XStore theme CORE plugin from you.
I did contact the author, he said that this was NOT a problem with the plugin, but with the XStore theme CORE plugin from 8themes(aka, you). ;
wp-content/plugins/et-core-plugin/app/models/customizer/functions.php:2213