By default Ninzio themes come with Visual Composer Front-End Editor disabled. This is needed, as Ninzio themes have custom elements (like carousels, progress bars etc.), that extend Visual Composer. Visual Composer Front-End Editor was designed for core Visual Composer elements, but not for custom elements, like Ninzio elements, and this is the key point, why Ninzio themes can not integrate their elements with Visual Compose Front-End Editor.

 
But if you need Visual Composer Front-End Editor, you can enable it by removing the code bellow:

vc_disable_frontend();
 

This code is located in you theme folder >> includes >> ninzio_vc.php file at line 3