You probably cannot attach you aia files because you use on or more extensions. You can either remove the extensions and post the aia or you can post an image of your Blocks Francesco.
Without an image posted to the Forum, it is impossible to give advice. Here is a huge guess, do you use a custom app icon? If the icon (actually a jpg or png image) cannot be larger than 96x96 pixels. If you use a larger image, either use no custom image or make the image smaller and your app might install. A second guess is that in the Android device settings, you are not setting the settings to allow sources other than Google Play Store...
Settings> System >Security >Unknown sources Check the Unknown sources option
Did this help?
Regards,
Steve