Thanks for coming back to us and sharing some updates about this banking issue, @azjb.
While QuickBooks is just a receiver of your bank feeds, the connection authentication is something that is out of our control. This security is controlled by the financial institution you connect in QuickBooks.
Users usually get those mentioned errors if the F.I. requires additional security requirements. While researching the issue we found that the bank website is prompting for OTP during each login attempt for security purpose and our product will behave the same way as per FI website and thus it is prompting for OTP in each login attempt (and /refresh ) for security purpose. If your bank or FI asks for an OTP, get your OTP (on a device, through text, call, etc.), the only workaround is to enter the code each time you see the errors.
I'm leaving the following links to help explain the error messages you're getting and how to handle them:
This thread is always open for updates and additional concerns. I'll be right here if you need other help too.
Thank you everyone for your replies... Actually, turned out to be something far more simpler... In order to keep the connection open with American Express, I needed to switch the connection to "American Express Business Credit Card (US)" and now everything seems to be working okay. Please note that there are several choices when setting up an American Express card, but for me, this setting worked.