Credit card expired

Have you tried signing out of your Apple ID and back in to see if that updates the payment method?

If necessary, contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide 

Apple Support schedule phone call      

If necessary, try Twitter

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.

If it isn't updating you might remove the card as a payment method and then add the same/updated card as a "new" payment method.