Utilize the trial version of MT Online to isolate the issue. It is designed to import into any bank or credit card in QuickBooks Online, so there is no specific setting needed. If the same error persists, there is an ongoing problem at your bank or connection.

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Hi monty-bipolarsup,

Welcome to Community!  Having the ability to update your transactions is a vital part of your daily bookkeeping tasks. QuickBooks Online is currently experiencing a connectivity issue with your financial institution. Our Development Team is working diligently, to get this restored as soon as possible.  In the interim, you can manually upload your transactions following the step-by-step instructions in this article.

If you'd like to be notified when the issue is resolved, please contact us outside of Community, so we can set this up for you.

Schedule a Callback or start a Chat: click (?) Help in the upper right in QuickBooks Online > enter "Contact support" > hit Contact Us > provide a brief summary of your situation > hit Let's Talk > choose Get a callback or Start a Chat.
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Support hours are from Monday to Friday between 9 a.m. and 8 p.m. ET.
 

If you have any other questions or concerns, feel free to reach back out.  We're here for you!