Unable to renew my iCloud subscription

if it was me then I would try

If your payment method is declined in the App Store or iTunes Store - Apple Support

or reach out to their support

 Get Support (apple.com)

And or

 Contact - Official Apple

Support

And or

Contact - How to Contact Us - Apple

Starting with perhaps the most important - as not all Payment Cards are accepted:

Payment methods that you can use with your Apple ID - Apple Support

If you only have a single payment method registered on your account, you must add another card before you can remove an existing entry. With two or more registered payment methods, you can arrange them in the order that they will be used.

If you need to change or update your Apple ID payment method - Apple Support

Many find having two registered Credit Cards to be helpful. If for some reason a subscription or other payment fails with your primary payment method, the payment will instead be made against the other Card. Card payments can and do fail for a variety of reasons - such as a temporary block on an account, and out of date card, or a technical issue with the Card issuer. Having an alternative registered payment method should ensure that services are not interrupted due to a failed charge to your account.

Change, add, or remove Apple ID payment methods - Apple Support