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After looking further into the 590 error that occurs when trying to link a Bank of America account with QuickBooks Online, I've discovered that there's an on-going investigation on this matter. Our Engineers are working hard to resolve this issue as soon as possible. If you'd like to receive email updates about this problem, you can contact our Support Team to get added to an affected user's list. Here's how:
Press the Help icon.
Pick Contact Us at the bottom of the pop-up page.
Give a brief description of your banking issue and then click Let's Talk.
Scroll down and choose to Get a Callback.
Afterward, you'll receive an estimated time of when they'll be in contact with you.
Keep us updated on this problem here in the Community. If you have any other questions, don't hesitate to ask.