I had the same issue. But I found that it was due to another plugin.
Activating wordpress debug i got this msg:
Undefined variable: _SESSION in /var/www/my.wordpreess.site/wp-content/plugins/custom-database-applications-by-caspio/classes/class-datapage-loader.php on line 4
I deactivated the Casio plugin, then the Content Control plugin was able to activate itself.