Hi MLJ2,
Congratulations on successfully connecting your credit card account. Let’s check to see why your transactions weren’t downloaded.
Clicking Update on the Banking page refreshes your connection and forces the system to download your transactions. It's also a way of knowing certain connectivity issues between your account and QuickBooks. When you click the said button, do you receive an error message or a code? If yes, please let me know about it and click the code in Step 4 of this article for more information and for the steps to resolve it: What to do if you get a bank error or can't download transactions in QuickBooks Online. However, if you don't get anything, please follow Steps 2 and 3 of that article.

Speaking of credit cards, multiple cards with a parent-subaccount setup are treated differently because only the parent or the sub-accounts will provide feeds. Therefore, you need to ask your bank which level has online banking feeds, and that's the only account/s you connect to QuickBooks. Learn more about bank or credit card subaccount setup.
Lastly, an alternative way of bringing transactions onto the Banking page is through manual uploads. Here's an article for more details: Manually upload transactions into QuickBooks Online.
Feel free to share an update after doing the steps in the first article I shared. I'm just right here to continue helping you.