I have Visual Studio 2013 with no plugins or anything fancy. Whenever I'm coding, every so often (maybe once every half hour) intellisense randomly stops completing my sentences or popping up at all when I press Ctrl+Space.
I have tried Tools->Import and export settings->Reset all settings but it did not help. The issue came right back.
The only thing that solves it for me now is to close VS and reopen it. But as you can imagine, this is extremely frustrating.
I was having the same problem and this seemed to work for me.
Basically, go to Tools >> Options >> Text Editor >> All Languages >> General and make sure that both Auto list members
and Parameter information
are checked (not the half-checked/square state).