visual composer not working

My visual composer is not working. I made the change to highend from another wordpress theme. After a couple of days, a page that I had set up would not appear, but kept showing a “404” error. i had it fixed and it worked for a few days and stopped. Then the page was showing properly but only if the viewer was logged into the control panel. Then it stopped again.
I had to take the page down because it was the contact page for my business and we were losing new clients. But how do I get visual composer to work now? and how to check and fix this problem as I fear that more pages will show this error since it seemed to work intermittently.