Let me guess, VC stopped working after you updated your Wordpress to 4.5?
Jupiter 3.9.3 has older (read: very very old) version of Visual Composer that is not compadible with Wordpress 4.5.
Basically you have two options:
Update your theme to a 5-th generation of Jupiter.
That would mean some work if you have any customisations in the child theme as Jupiter 5 uses different folder structure.
Update to Jupiter 4.5.
Artbees has released a legacy version of Jupier that has number of 4.5. This version has an updated Visual Composer that should support Wordpress 4.5. But please bare in mind that Artbees probably wont support 4-th generation of Jupiter forever and eventually you have to keep up with life and update to the latest version of Jupiter (currently 5.1.3.).
As @ben_childs noted, Jupiter 4.5 can be found inside Jupiter files that you download from themeforest.
PS: And dont forget to backup before you update anything.