I'm here to help connect your new bank account to QuickBooks Online (QBO).
Before anything else, did you receive any error messages when trying to add your new bank account? Any additional information would help us provide the best resolution to resolve your concern.
In the meantime, let's try accessing your QBO account using a private browser and add your new bank account from there. There are times that the browser stores frequently accessed data, thus causing QBO to act weirdly. Press this shortcut key on your keyboard to open a private browser:
Google Chrome: Ctrl + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Safari: Command + Option + P
Once logged in, go back and try to connect your new bank account. If this works, it means that you need to clear the browser's cache so the system can start fresh. If you get the same result while using a private browser, I recommend switching to a different one.