(SOLVED)Android: "App not installed."? Can't install Android APK File On Android Device?

Hi,

I can export an Android APK file just fine from current Godot 3.x on Windows 10.

When I try to install the exported Android APK file on my device(Samsung Galaxy S7 Edge Smartphone) I receive error: "App not installed."?

I don't know how to troubleshoot the above, please help, thanks!

issue with the Android keystore.