I can't buy a premium subscription from google play

[Matias Orson 0]

Hi, I'm having some trouble trying to buy a premium subscription from google play on my Moto X, it's says that "It's not qualified", but I have enough credit in my account to buy, I want to know why I can't buy and if it's have a way to buy from google play because I already used the gift card from the google to put some credits...