If you are unable to make a purchase, it could be because your credit card has expired and you have a subscription payment which is past-due.
To pay for your past-due subscription:
Sign in to Services & subscriptions with your Microsoft account.
Find your past-due subscription in the list and select Pay now. Make sure you're signed in to the Microsoft account associated with the subscription that's past due.
Check your payment method. If needed, you can update your payment method(if your credit card, PayPal, or other online payment service has expired, update it with the new expiration date) or add a new payment method(if your payment option isn't valid or you want to change it, add a new way to pay). For more help, see Change your Microsoft account payment method.
Once your payment option is set, select Next to make the payment.
Note: Gift cards, subscription cards, or your Microsoft account balance can't be used to pay for a past-due subscription.