If you did not / could not use your Simple Delivery label,  but used your own,   you cannot now add any new tracking,   eBay suggest sending the buyer a message with those tracking details.  If a case is opened later for item not received,   you will be able to add those tracking details.

A refund is sent to whoever paid for the SD 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.

Your payout will be held for a minimum of 14 days.

@jarbrovis