There are different reasons why you can't connect your bank account to QuickBooks, Roslyn. It's possible that:
Before we do any troubleshooting steps, I'd recommend reaching out to your bank. This is to verify if they have a website maintenance or added security features.
After that, let's ensure we have a strong and stable internet connection. Though cache files help websites load faster, they can also cause interruptions when piled-up on your browser.
We can do browser troubleshooting steps to get rid of any cache-related issues:
Let me know how this goes. Additional details such as error codes/messages and the name of your bank would be much appreciated. Thanks in advance!