Hi there,
It's vital you're able to update your credit card details so you can enjoy the benefits of using QB Online. Don't worry, I'll be happy to steer you in the right direction.
First, I'd like to start off by doing some troubleshooting to determine if this isn't a browser related issue. When was the last time you cleared cache and cookies on your browser? Doing this will help fix most issues the site may be having. Here's an article which shows you how to do that: How to clear Cache and Cookies. Let me know what happens after you clear cache and cookies.
For reference, check out this article which shares more info on how to:Update the payment method or information for your subscription. Give this a try and if you need further assistance, I recommend contacting our support team using this link.