The Viewer, at best, lets you see what your app might look like. It simply shows whatever is being done on the PC that is broadcasting.
But, if you are trying to test something on an iOS based device, unless you have a Mac of some sort to build your own, you are sort of stuck with the Viewer.
Although you might be able to get the Unsigned AppGameKit Player (from your 'My Products' TGC download page) to work.
If you are testing on an Android device, download the AppGameKit Player from the Google Play Store.
No matter what you are using on your device, you need to make sure that both it and your PC are on the same network.
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master