Could it be?
I tried and it works fine on a PC, but none of my successes in a mobile device (ipad, nexus 7, samsung galaxy S3, Kindle fire HD ...)
Browser support for the fullscreen API is actually very poor according to http://caniuse.com/#search=fullscreen
If you really need to use the full screen for your application, you should find an alternative for mobile users.
This Javascript hacker can help you: http://mobile.tutsplus.com/tutorials/mobile-web-apps/remove-address-bar/