Sign your Flutter app with upload key (App signing by Google Play)

I had the same issue, heres the workaround i used:

• Go to Android Studio
• Open your project "android" folder
• Go to Build -> Generate Signed bundle or APK.
• Create your key store if you dont have
• Check "Export encrypted key for enrolling published apps in Google Play App signing" IMAGE
• Use the output bundle ;)

The singing process works as described by the flutter documentation here. Regardless of whether you are using Play App Signing or not.

When opting into Play App Signing the app is being signed twice. Once by the developer with an upload key and once by Google with the app signing key. The advantage here is that it won't come to the point where the developer can no longer update their app because they lost the app signing key. Should you loose the upload key, it can be revoked and replaced using your Google account while still being able to release new versions of your app as the app signing key is still held securely by Google.

This android developer article explains in more detail how Play App Signing works.

I had the same issue, and this is what worked for me: https://developer.android.com/studio/publish/app-signing#enroll

As described earlier in this page, Play App Signing is the recommended way to sign your app for distribution through Google Play. The steps you need to take in order to opt in your app depends on whether your app has not yet been published to Google Play, or your app is already signed and published using an existing app signing key.

To opt in an app that has not yet been published to Google Play, proceed as follows:

1. If you haven’t already done so, generate an upload key and sign your app with that upload key.
2. Sign in to your Play Console.
3. Follow the steps to prepare & roll out your release to create a new release.
4. After you choose a release track, configure app signing under the Let Google create and manage my app signing key section