Some versions of Android come with a non standard "launcher" that doesn't obey the de1app's request to make a desktop icon.
To work around this problem, install launcher3 https://github.com/amirzaidi/Launcher3
and make it the default launcher.
Then when you run the app that creates the de1app icon, it will work:
How to Reset Your Tablet and Reinstall the Tablet Software (Video) - Decent Diaspora