'Use Visual Composer' option missing when editing project

I’m using the plugin in a theme package ‘Structure’ from ThemeMove and according to them I should have an option to use the ‘Visual Composer’ page builder that is included in the Theme, to build my projects. This option should be in the ‘project details’ section, just above the product line.

However, this screenshot shows that this option is missing. Is this a theme issue or is something missing in the ZIP file of the plugin? Would it be possible to make this a standard feature, that is hidden if the Visual Composer plugin is not installed?

https://www.ads-software.com/plugins/projects-by-woothemes/