You may need to reset the design for completed orders and send the link for customization once again to your customer. You can make it via the Reset Design button in the order details page in your Zakeke back-office (see below).
IMPORTANT: the Reset Design button deletes the previous design PERMANENTLY. Be careful when you use it as you won't be able to recover the design that you delete.
This button is displayed when the status is Complete:
After clicking on Reset Design the order returns to the status NEW and you will see only the button Show in the designer (see below)
Now it's possible to send the link to customize the design again to your customer.