Important: all Pro users should install the new version.
Thanks to Debo Ogunrinde, I identified a problem in the Pro version of the "KC s2M+MC" plugin. It was not a defect in the original logic, but changes in newer WordPress versions prevented some new users from being created. The compatibility problem has been fixed, so please download and install the update.
To preserve your options, you can replace the plugin file through FTP. Alternatively, use the standard process: deactivate and remove the old version, then install the new one.
Have a good day.