If you click into this order, click into the SKU on the orders page that is showing as 'missing customs data', an inventory pop-up will come out on the right-hand side, press 'actions' and 'edit', scroll down to Customs Data and you will need to add/edit the commodity code (sometimes also referred to as a Harmonised Code or HS code for short) then press 'save'.
Example:
Did You Know? Fedex require a Commodity Code to be a minimum of 8 digits long otherwise it will reject Hutch to be able to book a label.