Have you marked it paid and dispatched? This has to be done only on the Seller Hub now, here:
https://www.ebay.co.uk/sh/ovw
go to Orders >> Awaiting Postage / Print Postage label, and then click the box on the left of the item.
https://www.ebay.co.uk/sh/ord/?filter=status:AWAITING_SHIPMENT
From the Postage tab above, use the drop down menu there, if the option to mark as collected is not there, then select Mark as Paid and Mark as Dispatched.
