If a charge isn't approved (for example, the card is declined), the subscription becomes past due and you get email notices asking you to fix it. There is a grace period of a few days before access is fully blocked, and during that time a banner prompting you to fix your payment appears at the top of the app. Click it to pay the open invoice directly, instead of subscribing again from scratch. If the grace period ends without payment, access is blocked until you pay the outstanding charge.