If you have problems with your payment method and you need to update/add new cards, make sure to do it before the Subscription expires. 

The “Manage payment method” button in your Active Subscription page is available from the activation of the Subscription till its last day of validity.

Please note that the imminent expiration is notified to you by email few days prior.

In the case the Subscription expires before you update your payment method, you can only close the expired Subscription and purchase a new one, or charge the current payment method, if there is one registered, to renew the current Subscription.