I created a shop button in my project . when i pressed it shop menu opens

I added a script to shop_open

And added this script to the buttons like (2 coin, 3 coin etc).

and whenever i pressed the button the coins needed to be bought ,but it didn't happen.
So i created a IAP singleton(autoload) script like






But when i press the buy button ($1) , i get nothing output.
nothing is printed like purchase is cancelled or bought .
Can anyone help me setting up the IAP in my project ?