In-app review interface does not launch in Android

I am trying to integrate the in-app review library from Android, as described in the following link.

https://developer.android.com/guide/playcore/in-app-review/kotlin-java

From this link, I am using the following code.

private void showRatingUserInterface(final Activity activity) {
    final ReviewManager manager = ReviewManagerFactory.create(activity);
    Task<ReviewInfo> request = manager.requestReviewFlow();
    request.addOnCompleteListener(new OnCompleteListener<ReviewInfo>() {
        @Override
        public void onComplete(@NonNull Task<ReviewInfo> task) {
            if (task.isSuccessful()) {
                ReviewInfo reviewInfo = task.getResult();
                Task<Void> flow = manager.launchReviewFlow(activity, reviewInfo);
                flow.addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task2) {
                        // do nothing
                    }
                });
            }
        }
    });
}

Android also describes how to test the in-app review library, as shown in the following link.

https://developer.android.com/guide/playcore/in-app-review/test

I followed the guidelines from the links above, however, the in-app review interface is never launched. In more detail, I've performed the following actions.

• Added play core dependency version 1.8.0 to the build.gradle file.
• Released an internal test of my app in the Google Play Console, including the code shown here above. This function is called when my game is finished.
• Cleared review in the Play Store of this application from my test account.
• Downloaded my app from the Play Store with my test account.

Has anyone an idea what goes wrong here?

Apparently, I was using the internal test incorrectly. Now that I've setup the internal test correctly, it works! I've followed the steps from the following link.

https://support.google.com/googleplay/android-developer/answer/3131213