Thank you for adding your first post here in the Community, Joanne. I'm here to take care of your concern about linking your credit card account to QuickBooks Online (QBO).
Your bank may have an additional layer of security reason why QuickBooks asks you for security steps to link your account. If you have 2-Factor Authentication with your online banking, your password is the first factor to log in, and then the text message code is the second factor. If you encounter issues with the security process, you may connect with your bank or to our designated Support for further assistance. This way, they can look into your account securely and review the connection between QuickBooks and your financial institution.
For more tips while handling banking-related issues with QBO, you can check the links below: