Something to do with it not working with iPhones? I think its because the resolution because it works on iPad. Maybe try it on a iphone 6 or 6S as it has a bigger screen?
Basically, it all goes on what sort of device you own. The newer Androids can do this because of bigget screens (that's the problem as far as I know.). @Jordan said to me that he could comment just fine on his phone which is a Galaxy S5