Important! Please all Pro users, install the new version.
Thanks to Debo Ogunrinde, I find a bug in "KC S2M+MC" plugin, Pro version. Well, not a bug, but because of changes in new WP versions, some new users was not created. Fixed, so please download the upgrade and re-install the plugin.
To save your options you can just update the plugin file by FTP. Or, just go by usual way: deactivate and uninstall old version and install the new one.
Have a good day to everyone! :-)