The only thing that worked for me from the advice from the support agents was to completely de-link the account and then re-add the account in QB.

However, this worked for about 3 days and I'm getting the error again. When I go to de-link the account, I noticed that my email address is default populated in the username field for the bank login. I noticed this previously too. I suspect QB has a bug where the bank username is being over written by the email address and causing a login/integration error.