Leonardo Game Controller not showing up in HTML5

I have a great USB game controller based on Leonardo using this tutorial:

When I look at control panel/devices and printers/game controller/properties, I can see everything is active and working.

However, I cannot get the game controller to show up when I go to this website to check it working in a HTML5 browser:

?

I have another USB game controller that works fine. How can I get the Arduino one to work?