There's no denying there are issues with Simple delivery not ' delivering' a perfect service and DPD collections have been a failure for many. We are told eBay are aware.... 🤔 !
Meanwhile as you have not used a different service you cannot change the tracking so it's advisable to send the buyer a message with those tracking details, but should later a case for item not received be opened, you are able to add that tracking into the case details.
@consumermania