This error may be caused by several reasons.
Here is the list of requirements for the Google IAB testing.
Prerequisites:
- AndroidManifest must include “com.android.vending.BILLING” permission.
- APK is built in release mode.
- APK is signed with the release certificate(s). (Important: with “App Signing by Google Play” it only works if you download directly from GooglePlayStore!)
- APK is uploaded to alpha/beta distribution channel (previously – as a draft) to the developer console at least once. (takes some time ~2h-24h).
- IAB products are published and their status set to active.
- Test account(s) is added in developer console.
Testing requirements:
- Test APK has the same versionCode as the one uploaded to developer console.
- Test APK is signed with the same certificate(s) as the one uploaded to dev.console.
- Test account (not developer) – is the main account on the device. (Main account might be not necessary – according to @MinosL comment)
- Test account is opted-in as a tester and it’s linked to a valid payment method. (@Kyone)
P.S: Debugging with release certificate: https://stackoverflow.com/a/15754187/1321401 (Thnx @dipp for the link)
P.P.S: Wanted to make this list for a long time already.
Thnx @zlgdev, @Kyone, @MinosL for updates