By default we do not load all module install in visual composer. Because some are non standard module which do not follow standard Prestashop frontend controller system. Which cause problem in front end. That is why we only load the default Prestashop module and exclude payment modules from our vc pop up.
Some time you may need to load some thirdparty module to use in vc pop up. From visual composer settings you can include or exclude any module from vc pop up.
Visual Composer -> General Setting