Having Trouble in Apple Store

Perhaps you have something to adjust...

See this support guide: If your payment method is declined in the App Store or iTunes Store - Apple Support

If you're sure that your payment info are okay, contact iTunes Store Support and explain your problem, filling out and submitting this form: iTunes Store – Contact Us – Apple Support

Regards

Giulio

It is probably wanting you to confirm your payment method. See if the CVC section is blank and if it is enter the number and save it.