Flutter - IAP items not appear using plugin example

I try to run IAP (in-app-purchase) example apps that provided by flutter here: https://github.com/flutter/plugins/tree/master/packages/in_app_purchase/example

I follow all step, except upload signed App Bundle instead of APK to Alpha Phase at Google Play Console.

However, when i open the screen example, it said warning:

Consumable, Upgrade, Subscription Not found, This app need special configuration to run. Please see example/README.md for instructions.

so, all of my IAP items that has been created at play console not appear.

Any idea to solve ?

Screenshot:

from Flutter - IAP items not appear using plugin example