Thanks for dropping by here in the Community. Let me assist you with connecting the new account in QuickBooks Online.
Before you can connect, QuickBooks will request permission from the bank's website. Since you're getting an error when performing the process, there may be an ongoing issue with the connection between QuickBooks and your financial institution.
However, I recommend performing the basic troubleshooting to isolate the issue. I'd first suggest logging into your QBO account using a private browser.
It doesn't store data in the cache. Thus, it's a great way to isolate browser-related issues.
If you're using Mozilla Firefox or Microsoft Edge, press the CTRL + Shift + P shortcut on your keyboard. For Safari, hit Command + Shift + N. Press CTRL + Shift + N if you're using Google Chrome.
From there, please connect the account again. If it works without getting any error message, let's clear your browser's cache to have a clean slate, so it'll function efficiently.