Fontawesome source stopped working

Basically, the icon numbers are showing instead of the icons themselves.

For example in the navigation you can see ‘e801’

further down the page the cart icons, next to Add to Cart also show the icon number.

I can see fontawesome when I view source, but it seems to have stopped working.

Switched theme and it worked again so must be to do with the theme settings somewhere?

The page I need help with: [log in to see the link]