Intellisense in IntelliJ no longer working

Question

I\'m currently running IntelliJ IDEA 13.1. While running IntelliJ 13 intellisense/autocomplete stopped working. I tried upgrading and it still doesn\'t work.

I can e

Answer 1

For me it was because I did not have a folder marked as Source Root (it appears in blue).

To fix, right click your root source directory -> Mark As -> Source Root.