I can't..

Hello there,

Thank you for posting here on the Xbox forums. What error message do you get? Have you tried to pay the past due balance using this link here :

How to pay a past due balance on an Xbox subscription

Nothing, just want to pay pending subscription with gift card, and have the amount of money you need

Were you using the link
on this page to pay the balance?

yes

Were you using the link
on this page to pay the balance?

yes

When your Xbox subscription is suspended and you have an outstanding balance, you must pay the balance in full to continue using it. Here’s how to pay your past due balance online:

1. Sign in to your Services & subscriptions page with your Microsoft account.
   Note If you don't know your Microsoft account email address or password, use the
   
   Lost Account Solution or the
   Lost Password Solution.
   
2. Find your past due subscription in the list. The amount past due will be in red.
   
3. Select Pay now, and then follow the instructions to pay the balance due.
   

Note Adding a prepaid code will not settle the balance you owe. You need to settle the outstanding balance using the steps above before redeeming your prepaid code.

hai controllato se la carta contiene denaro? hai provato se ci sono arretrati di pagamento di altre cose?
Suggerisco di pagare direttamente sul sito e non sulla console