After a decline, the system will automatically try again in 5 days. If you are within that time, you can update your card on the web app by navigating to:

Home page > My Account > Add New Card. 

Enter in your new card information and click save. The system will automatically use this card on the second try, and your service will remain uninterrupted.

If the system has already tried twice and you are locked out, you can still update. Log into your account, and on the lockout page click on 'subscribe'. Follow the prompts to select your plan and enter in your new card details. The system will reinstate your account with all your data using the new card, and continue your subscription from that date.