In-App Purchase Fails with "BillingResponse.itemUnavailable" After Unpublishing App (Flutter)

Question

I have a Flutter app that uses Google Play Billing for in-app purchases. Everything was working fine until I unpublished the app from the Google Play Store. After that, my in-app purchases stopped working in test builds.

Issue: I can successfully fetch product details using queryProductDetails, so the product ID is correct. However, when I try to purchase a subscription, I get the error: BillingResponse.itemUnavailable The item you were attempting to purchase could not be found.

Questions: Does unpublishing an app affect in-app purchases for Internal Testing builds? Are there additional steps required to re-enable IAP for an unpublished app? Could there be a Google Play Console setting preventing purchases even though product details are retrieved successfully? I’d appreciate any insights or solutions to resolve this issue. Thanks!

What I Have Tried:

• The app is still available in Internal Testing in Google Play Console.
• The Product ID is correct, and I can retrieve product details successfully.
• My Google account is added as a licensed tester.
• I am using a signed release APK uploaded to Internal Testing (not a debug build).
• Cleared Google Play Store & Play Services cache on my test device.
• Verified the subscription is Active in Play Console (not in Draft or Inactive state).