[de.dwd.warnapp] Existing Google Play license can not be restored

Affected app
Name: WarnWetter
Package id: de.dwd.warnapp
https://play.google.com/store/apps/details?id=de.dwd.warnapp

Describe the bug
When trying to restore an existing license by tapping "Full version" on the main activity, microG displays the message "You already own this item.".

I assume this means that the app is trying to initiate the IAP for the full version, where real GMS would probably return some kind of "already bought" message to the app.

To Reproduce
Steps to reproduce the behavior:

1. Finish app setup
2. Click on "Full version"

Expected behavior
The app would restore full access as the purchase has already been made before

Screenshots

System
Android Version: 14
Custom ROM: crDroid 10.2

microG
microG Core version: 0.3.1.240913
microG Self-Check results: All ticked

Additional context
I am happy to use development builds in order to test if the behavior is fixed.

Start by reproducing the WarnWetter purchase flow on Android 14, following setup and the Full version action until microG shows “You already own this item.” Read the Play Services purchase and license-restoration implementation that handles this flow. Done means an existing WarnWetter purchase restores full access instead of displaying the error.