Installing apk files on Kyocera Dura XE (flipphone running android)
You'll get more information about your problem by using:

adb logcat -v * &gt; mylog.txt

you'll find the file mylog.txt in the directory where you've executed the adb command. (you can share it to help you figure out what's the problem)
The problem is:
The same package name (APK) exists on Android device with different signature.
When you try to install the same package (APK) again signed with a different signature:

Example:
The first APK was signed with Debug keys, then the APK you're trying to install is signed with Release keys

The solution is:

Uninstall the old package (APK) manually from Settings&gt; Apps

or from the CMD shell, run:

adb uninstall your.package.name