I am unable to update credit card for billing?

Hi michelle-herring. The best way to get your issue resolved would be to reach out to the QuickBooks Online care team so they can review your account. Since the Community is a public forum, I'm unable to review your account without asking for sensitive information. 

Reaching out to our QBO Customer Care Team ensures that you'll be able to get back on track with using QuickBooks. I recommend logging into your company to view the support details:

1. In your company, go the Help icon to choose Contact Us.
2. Type the issue/topic under the What can we help you with section and then hit the Let’s talk button.
3. Scroll down to select the Get a callback option and then enter your contact information.

For additional information about the declined credit card, check out the following article. It also contains a list of some of the possible reasons:

Credit card declined for QuickBooks Online subscription.

The community is always happy to help. So if you need anything else just leave a reply below. Have a great day.