Why can’t I add payment card to my iCloud?

Hi muktar67,

While the precise nature of what you're attempting isn't clear, here are a couple of possible suggestions based on what you might mean:

1) If you're attempting to set up Apple Cash, then per Set up Apple Cash you must meet these requirements:

"What you need

• Be at least 18 years old and live in the United States.
• Have a compatible device with the latest iOS, iPadOS, or watchOS.
• Set up two-factor authentication for your Apple ID. 
• Sign in to iCloud with the same Apple ID on any device that you want to use to send or receive money.
• Add an eligible debit card in the Wallet app, so you can send money."

2) If you're attempting to add a payment method to your Apple ID account, then If your payment method is declined in the App Store or iTunes Store or If you need to change or update your Apple ID payment method may be more appropriate resources based on the action you're trying and the result you're seeing.

Regards.