Hello. I’m french. Sorry for my english. I have exactly the same problem. I installed the visual composer addon plugin but it’s IMPOSSIBLE to ACTIVATE this plugin.
The message I have :
Fatal error: Call to undefined function add_shortcode_param() in /var/www/clients/client2/web5/web/wp-content/plugins/showcase-visual-composer-addon/includes/vc-showcase.php on line 6
and and other message in the plugin description :
“Important: You must need update the your .htaccess”.