How to properly set up a response after payment in Android?

Question

Android

I set everything up as per the documentation, and everything basically works, however, from time to time after the payment, a response from Google does not come, this happens immediately in a row from several users. Has anyone experienced something similar?
I use the In-App Billing v.3 library, and the answer itself comes in the IabHelper class

Answer 1

Which one exactly? Which are built into the application or which are through google pay