If you haven't done so already escalate your case. You should have been given a date to do that in the email you got from ebay when you started it. It's usually at least 3 working days later. Go to the return case via the link on the ebay message, click on Case Details > Respond to Case > Escalate This Case > Submit.
If you've done that the only reason you wouldn't get a refund (assuming you're within the 30 day deadline) is if the postal tracking shows delivery even if you haven't received the item. ebay will always go by the tracking.
