If you need to undespatch an order, please do the following:
Click Orders then Overview.
Search for the order.
Tick the order.
Select Cancel from the Bulk Actions dropdown.
Click Go.
Tick the order again
Select UnCancel from the Bulk Actions dropdown.
Click Go and then the order will be in NEW status.
Note: If you cannot Cancel the order, please review the Cancel a Despatched Order article.