You have to comply with everything on the list to qualify for a refund for an unused Simple Delivery label.

https://www.ebay.co.uk/claims/simple-delivery/refund/seller

To process your refund, we'll verify the following:-

The label was paid for by you (you offered free shipping to the buyer).
The refund request is created within 14 days from the item's sale.
The label wasn't used within 14 days of the item's sale.
The package was delivered using a different tracking number.

If your request meets all these conditions, you'll receive a refund for the shipping cost. Please note, it may take up to 14 days for the refund to be processed.

Oh, and one more thing, as Gladys Pugh used to say... if the buyer has paid for the postage, they will automatically receive a refund for the unused Simple Delivery label... 🤖