Hello,

You can navigate to Appearance > Install plugins and update. If the automatic update does not work, update manually:

1. Upload the recent version of the theme from the Themeforest account.
2. Navigate to Plugins and deactivate the current plugin, you will see the “Delete option”, delete the current plugin
3. Upload the plugin archive from theme/inc/plugins/js_composer via Plugin > Add new > Upload > install > activate

If the issue still exists then please send me the WP admin login details of your site so I will check and solve the issue for you.

Best Regards