I already published my app straight to the public 8 hours ago, but my my in-app purchase don't work at all. It says "Authentication is required. You need to sign into Google Account".
Do I have to wait longer or publish my app to alpha or beta channel first in order to get the in-app work?
Based on the document: Testing Your In-app Billing Application
To ensure that In-app Billing is functioning correctly in your application, you should test the application before you publish it on Google Play. Early testing also helps to ensure that the user flow for purchasing in-app items is not confusing or slow, and that users can see their newly purchased items in a timely way.
The Google Play Developer Console provides several tools that help you test your In-app Billing implementation:
To test in-app billing, you need to publish your app to an alpha or beta channel in Google Play.
After you publish an app to an alpha or beta channel, it can take a few hours for the app to be available for testers. The version code of an APK on a test device must match the version currently uploaded to the alpha or beta channel on Google Play.
Also, it would be helpful to check if you have properly implemented In-app Billing with this links:
Important: Apps using in-app products must declare the
com.android.vending.BILLING permission in their APK manifest file. Without the
com.android.vending.BILLING permission, developers can only manage existing in-app products using the Google Play Developer Console and any attempts by the app to make In-app Billing purchases will fail.
Hope this helps!