Upload new APK to Alpha - failed

You can see from the error that there is no jar signature.Select both the checkboxes for signature versions (v1 and v2) in last step and then build the apk. It will work

I was getting this error when I updated to android studio 3.3, the solution was remove the build folder, and then try again.

I think that you probably simply accepted the default configuration settings during the APK signup process in Android Studio. This is ok most of the time, but might generate a slight confusion if you use Android 7.0+ Indeed from version 7.0, Android intruduces the new V2 Signature Scheme in addition to the "old" V1. The new scheme is supposed to offer faster app install times and more protection against unauthorized alterations to APK files, and it is therefore the default scheme in Android Studio's "Generate Signed APK" dialog box.

The problem is that Google Play in your case wants the V1 scheme to be applied, that is the JAR signing, rather than the APK signing as in V2. The Google Play documentation explicitly states that: "Although we recommend applying APK Signature Scheme v2 to your app, this new scheme is not mandatory. If your app doesn't build properly when using APK Signature Scheme v2, you can disable the new scheme.".

The solution that I have found in those cases is to enable both, as shown in the screenshot below. Once you do that the signed APK should be accepted without problems by the Google Play versions management system.

Generate Signed APK dialog box in Android Studio

This is the complete procedure:

1. in Android Studio, select "Build > Select build variants" and make sure that the "release" variant is selected
2. select "Build > Generate Signed APK" and enter the information about your keystore. I suppose that you have already created a signed APK in your previous try so these fields should be already set to the latest values. Click [Next].
3. the next screen is where you have to make sure to check both V1 and V2 as the signature versions, afterwards click [Finish] to generate the APK.

1. Build -> Clean project
2. Select the checkboxes for signature versions v1 and v2