Android App Not Install. An existing package by the same name with a conflicting signature is already installed

I had the same error message, but these answers did not help. On a 4.3 nexus 7, I was using a user who was NOT the owner. I had uninstalled the older version but I kept getting the same message.

Solution: I had to login as the owner and go to Settings -> Apps, then swipe to the All tab. Scroll down to the very end of the list where the old versions are listed with a mark 'not installed'. Select it and press the 'settings' button in the top right corner and finally 'uninstall for all users'

The problem is the keys that have been used to sign the APKs, by default if you are running directly from your IDE and opening your Emulator, the APK installed in the Emulator is signed with your debug-key(usually installed in ~/.android/debug.keystore), so if the previous APK was signed with a different key other than the one you are currently using you will always get the signatures conflict, in order to fix it, make sure you are using the very same key to sign both APKs, even if the previous APK was signed with a debug-key from another SDK, the keys will definitely be different.

Also if you don't know exactly what key was used before to sign the apk and yet you want to install the new version of your app, you can just uninstall the previous application and reinstall the new one.

Hope this Helps...

Regards!

 Go to Settings > Apps, find and open the app info. Then, open the overflow menu (3 vertical dots), and choose Uninstall for all users.

Go to Settings > Apps, find and open the app info. Then, open the overflow menu (3 vertical dots), and choose Uninstall for all users.