Why can't I subscribe after adding an ATM card to my Apple Account

It may take 24 hours for the account update to come into effect ...

or ... You could try Restart your iPhone - Apple Support (deletes temporary files, re-estalishes connections, may update recent setting etc., changes, and often restores order if something is not working as expected.)

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Else If needed:

See which payment methods Apple can accept in your country or region:

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

How to add an Apple Account payment method:

Add a payment method to your Apple Account - Apple Support

How to delete an Apple Account payment method:

Remove a payment method from your Apple Account - Apple Support

How to change an Apple Account payment method:

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