By default, Visual Composer may not be pre-configured or setup by your theme to allow Visual Composer layout editor to be used on all post types such as Products or Posts. You can change this using the Visual Composer Role Manager:
- From your WordPress admin, click Visual Composer
- Click the Role Manager tab
- From the Post Types drop-down, choose Custom, then check each of the boxes available and click Save
This will enable the Backend Editor button on these post types to enable the Visual Composer interface.