I'd like to make sure you're able to get into your account so let me guide you to the right support who can assist you further.
If you're connecting using the Direct Connect process, contact your bank and ask them whether you need a special code for sign-in credentials.
However, if they don't need a special code and you already tried out the steps in this article Fix OL and OLSU Bank Feeds errors in QuickBooks Desktop and still can't get into your checking account, I'd suggest reaching out to our QuickBooks Desktop Support so they can investigate this further.
All account-related concerns need to be directed to our phone support for security purposes. Unlike in this public forum, they have the tools required to perform any escalations in the system whenever necessary on your behalf. Here's how to reach us:
Go to Help, then select QuickBooks Desktop Help.
Select Contact Us.
Give a brief description of your issue, then select Let's talk, and then choose a way to connect.
You'll want to check out our QuickBooks Desktop articles if you need resources for any other QuickBooks-related concerns. I'm sure this will guide you in doing a specific task in the program.
I'm always around to lend a hand if you have more questions about QuickBooks or any bank-related concerns. Just tag my name in the comment section so I can assist you further. Take care and have a good one.