Hello
I built my app via intel xdk. it has the official IAP plugin . Before i used cranbeerygame IAP with the same problem
I uploaded the app to google play to test as Alpha
Published it
used a test account to purchase IAP
I get an error message "Authentication is required. You need to sign into your google account"
This message occurs only for my app i can purchase other apps on the store so its not an google play issue but something with the plugin/ build / configuration