Hello, nashnazril! Welcome to Apple Support Communities!
I understand you're seeing a message indicating that your American Express payment method is invalid. Rest assured, I will point you in the right direction.
I understand you're seeing a message indicating that your American Express payment method is invalid. Rest assured, I will point you in the right direction.
There are a variety of reasons why this may happen. The popup indicates that a different payment method must be used before you can continue.
Please reach out to our iTunes Store team for further assistance with your Apple ID: Contact Apple Support
Have an excellent day!