I've never used this project before, thought I'd get started now.
Just recently updated to the newest version of unity (now version 2017... instead of 5...) and just downloaded the 4.1.4 beta for hopefully better compatibility with unity 2017.
I'm working through the early parts of getting started part 1, and I can't see the green line gizmo path after setting up the grid graph and the AstarAI script and hitting play, then going back into the scene. Draw gizmos is checked and 3D icons is unchecked in the gizmos section.
EDIT: RIGHT after I posed this I saw it in the scene view while game was playing. I thought it was going to show while the game wasn't running... whoops!