Can’t purchases Icloud storage by apple ID balance

Hey there,

There must be a payment method in your account first and then you can buy using your Apple ID balance!

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

When you buy items or pay for subscriptions, Apple attempts to charge your payment methods in this order:

1. Apple attempts to use your Apple ID balance to cover the full amount.
2. If you don't have Apple ID balance or you don't have enough to cover the full amount, Apple attempts to charge your primary payment method. The primary payment method is at the top of the list in Settings on your iPhone. You can control which payment method is at the top of the list.
3. If there's a problem with the primary payment method, or if the primary payment method can't be charged for the full remaining amount, Apple attempts to charge your other payment methods in order from top to bottom. If none of them can be charged, Apple might try again.

See ☞ How apps, content, and subscriptions from Apple are billed - Apple Support