What causes this Android APK Upload error: “Non-upgradable APK”

Question

I have an Android APK in the Google Play store with an Target SDK of 23.

I have released a new version (same target SDK) and Google shows me this error:

If I

Answer 1

For those of you using Android Studio, I had this problem after upgrading from Eclipse to Android Studio and not configuring the gradle files properly.

Make sure the version code in your build.gradle in defaultConfig{} is correct.

...
defaultConfig {
    ...
    versionCode 373
    versionName "3.73"