This isn't the experience we want you to have when trying to download your American Express banking transactions, @LauraLH.

Have you tried the troubleshooting suggested by my colleagues above? If you're still getting the same error after performing them, I suggest contacting our Customer Support team. They have the necessry tools to take a closer look at your case and provide further troubleshooting. 

Here's how:

1. Open QuickBooks.
2. Proceed to Help, then choose QuickBooks Desktop Help.
3. Click Contact Us.
4. Give a brief description of your issue.
5. Select Let's talk, and then choose a way to connect.

Once everything is settled, you can start adding and matching your bank feeds transactions in QuickBooks Desktop: Add and match Bank Feed transactions.

Fill me in if you have further concern with managing and downloading your AMEX bank transactions in QuickBooks. I'm always around to help. Keep safe!