Error OL-393: The error message says that QuickBooks and the bank cannot synchronize data because details cannot be confirmed by the bank from QuickBooks.
QuickBooks Error OL393 mostly comes up when the user is not a regular user i.e. he uses QuickBooks after a certain period of time. The Bank refuses to synchronize with QuickBooks due to some security issues. The solution to this error is you can deactivate online banking and reactivate it but keep in mind that first, you D-sync your bank account from QuickBooks.
For any further queries call QuickBooks customer service +1-650-385-8069.