Quantity plus and minus buttons are missing

I’m using Fruitful with Woocommerce and in my instance the plus and minus buttons near the “Add to Cart” button are missing.
You can see them here how they are supposed to look: http://themes.fruitfulcode.com/fruitful/product/flying-ninja/.
And what they look like in my installation: https://docs.google.com/file/d/0B5AF5EUuJ3kodlR5Nmd3Q2dHclU/edit?usp=drivesdk

Do I need to activate them somehow?
It seems there is a script not loaded?

Any help is appreciated!

Chris