Billing problem
Update my payment method
iPhone 8, iOS 12
Question marked as
As suggested by the error message you got, contact Paypal and ask them about that problem.
Perhaps you need to change or input a new payment card using this support guide:
Change or remove your Apple ID payment information - Apple Support
If you get no help, contact iTunes Store Support and explain your problem, filling out and sending this form:
iTunes Store - Contact Us - Apple Support
Regards
Giulio