IAP How to make Fake-Shop buttons work?

I’m trying to implement IAP in my game.
All works, but when Fake Shop appears, I see two buttons: buy and cancel. But clicking on them does nothing. I Can’t close it, can’t buy. Is there anything I can do to make them work?
I’m trying the IAP 4.12.2 version - but nothing helps, now I’m on IAP 5.0.0-pre1. I rewrote the code, but the shop still appears with dead buttons.
Please help.