Hi Hari,
Please check in GTS Area Menu-> Legal Control Export-> Display Existing documents with the Sales order# as reference number. You should be able to see 2 items for your customs document here.
If you can see an entry in this list, open the document and check if the status of the sales order is red(blocked). If yes, release the order and then create the delivery.
If you need help in releasing the order, please post the error log that you see in GTS for your sales order customs document.
Regards
Dhilipan
