Problem installing app on Flytouch 9

Hi.
An app that works fine on Android 4.4 does not install on Android 4.1.1.
I've recompiled the app creating package following these instuctions https://forums.xamarin.com/discussion/20595/cant-build-apk-for-release.
When Apk is "run" on flytouch, the "installation" screen appears and remains on the display for an infinite time.
Do I have to know something else to build correct apk and install it for 4.1.1?
Thanks