Unity IAP Product.receipt always NULL in `IStoreListener.OnInitialized` in Android

What is the “Payment declined” in your first screenshot? Is that screenshot of a user, or your Developer dashboard? But in your case, the issue would not be in initialization, but in ProcessPurchase. Are you able to reproduce? Place Debug.Log statements in all your purchasing methods and IAP callbacks, and provide the device logs during your purchase test How To - Capturing Device Logs on Android