I see, looks like a Paypal/Play Store issue. Well, Google only allows the payment methods that go through their system, so it's either credit card, paypal, or a Play Store gift card (they sell them usually in department stores or gas stations). I am afraid, solving this is beyond my control, but if you added paypal as payment option very recently, then it may be a matter of simply reporting the problem and waiting for a day, maybe they'll sort it out.