Instead of creating a new account for every test, you can use the Play Billing Lab app provided by Google. Here’s how:
Download the Play Billing Lab app from Google Play. (Note: Make sure your Android device is running a recent version. For example, mine works on API 34.)
Open the app and configure the settings:
Set the region appropriately. Check the box labeled "Test free trials or promotional offers." Test your app with the same Google account:
Even if you’ve previously made a “test purchase,” this setup should now display the free trial offer correctly.
By the way, I’m facing a similar issue. Have you managed to solve this problem?