I am working a on basic Flutter 3.19.6 app, target android.
I can nicely use a Cognito user pool for authentication and attach otehr AWS permissions.
I can see the users being created in the Cognito user pool in AWS console.

I have followed the documentation tutorial carefully, completed

amplify init
amplify configure
amplify push

My pubpsec:

dependencies:
  flutter:
    sdk: flutter
  amplify_flutter: ^1.8.0
  amplify_auth_cognito: ^1.8.0
  amplify_authenticator: ^1.6.0
  amplify_storage_s3: ^1.8.0

My build.gradle:

   ext.kotlin_version = '1.9.23'

My app/build.gradle

    minSdkVersion 24
    targetSdkVersion  flutter.targetSdkVersion

I can build a debug apk, and run in emulator

flutter run

and here the authentication form works well.

However, if I do

flutter build apk

The first login/account creation is impossible and a ‘Network error message is displayed’
See:

I have tried also the following, it did not solve

flutter build apk --no-shrink