NOTE - This entire post is unconfirmed, just a guess
My entire forum just went down with a blank page and unfortunately stayed that way until I got the emergency support request. I did an analysis of the page load and saw that gravity insights loaded but nothing else could be seen. After testing turning off the gravity insights plugin, everything worked.
I just went to the gravity insights website - their site is down and has an "OK" on it - that's all. I am guessing that if the gravity insights site and service goes down, it is possible to take down your forum along with it.
Not blaming VBSEO, just that other customers like me got the service here and will likely have the same problem if this is, indeed, the problem.