We have a client that had the same issue around early November.  Nothing worked.  We tried adding a personal account just to see if it would bring over data and it did.  We assumed it was their bank.  They switched banks to Chase and everything was working fine until today.  QBO and the new bank stopped syncing again!  It's definitely on QBO side but can't get anyone to fix it.  They keep pointing to the bank but what are the odds it happened with two different banks.  Intuit, you've got a lot of angry customers.  Please do something or you will more than likely lose them.