Error: The account period has closed.

Occurrence: When attempting to import transactions into QuickBooks Online, the import fails with the error message The account period has closed.
Cause: QuickBooks Online has a feature to close the books which removes the ability to enter or edit transactions for a specified date range or prior to the closing date without dismissing an alert message. This restriction also applies to importing transactions using Zed Axis.
Resolution: In order to remove this restriction you will need to edit the closing date settings in the company settings in QuickBooks Online go to Gear icon > Company settings, the select Advanced > Accounting > Close the books or change the date of the transaction so it is not in the closed period.  It also may be caused by an inconsistency between you windows desktop short date format and that used in QuickBooks Online so please check the Date format setting too.