Yep, this is an issue many are experiencing you are not alone.
On last week's Weekly Chat with eBay Community Managers, this was announced....
' You can use your own courier if you wish. DHL are experiencing higher volumes than usual and are working on this to improve the service level. A refund request for the postage can then be made. '
If you are in this position and can use your own postage do so, and a refund for the unused Simple Delivery label is made this way:
Unfortunately, the system is thus, that is, once you trigger the SD label, it marks the item as dispatched! Maybe an explanatory message to your buyer explaining this may appease them !
@marbles1234567