It's a known issue, eBay are saying DHL are just not coping with the extra numbers involved, this statement from a Community manager a little while ago:
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.
Take the item to your PO use over the counter postage, then you can manually update the tracking, and use a laptop / PC for this. Chrome works well too.
- Go to "Orders Paid & Dispatched"
- Click on "View order details"
- Within the "Postage" section there's a small dropdown arrow next to "Track Package" - click on that.
- Click on the "Add tracking" option
- A box will come up with the current tracking number . Delete that and replace it with your trackin
For the unused Simple Delivery label:
- If you selected 'Buyer pays’ when you created the listing, your buyer will automatically be refunded for any Simple Delivery label that isn’t used after 30 days
- If you selected ‘Seller pays’ and offered free postage on your listing, you'll need to fill out the Request a refund for Simple Delivery form for the label that wasn’t used. Make sure to send your request within 14 days of your item selling. Also ensure you add the replacement tracking number of the service used, and it shows delivery.
@tridog3000