Verification required?

Your payment information must be accurate, up to date and match exactly what’s on file with your bank, including the current three-digit CVS number on back of the card. Call your bank to check if they are blocking payments to iTunes for some reason. If you still can’t figure out what the issue is, you’ll need to contact iTunes Store Support directly.

iTunes Store official support, including billing and verification issues

https://support.apple.com/itunes 

Was your payment method declined? If yes, see If your payment method is declined in the App Store or iTunes Store https://support.apple.com/en-us/HT203005