Why my restart button is not working?

I’m beginner simple making hat trick! Game
Via following official tutorials.
http://unity3d.com/learn/tutorials/modules/beginner/live-training-archive/2d-catch-game-pt2
I have problem in button.
Using unity 5.0.2f1.
The restart button is not highlighted and its not working.
What should i do?
I’m stuck there.
Please get to me back soon.

Add an EventSystem to your scene, as this is needed to perform interactions with the UI.