Menu was gone! Can not restore navigation menu from my web sit!

Dear SiteOrigin,

I constructed my web site using Vantage premium theme and works great during last 4 months since I made it last Jan.
Unfortunately, navigation menu disappeared suddenly after update several plugins couple weeks ago.
Although I tried to restore menu to appear home and other pages, I couldn’t.
Currently, I make it seen on side bar in website as a stopgap and seen as a collapse menu on mobile by using another plugin.

my site is ‘www.mutagenex2015.com’

Please help me how can I make menu seen on the website! This is our business site!

Thank you very much in advance.

James Ko.