There are a couple reasons an error can occur. The most common is when you've changed your username and/or password at your other bank. Here's how to fix it:
Fixing an error message for a linked external account in online banking
Fixing an error message for a linked external account using the U.S. Bank Mobile App
If you haven't made any changes, there may be a technical issue on our side collecting your account details. We will work to fix the issue as quickly as possible. Please check your account later for updates.