If you are on time, that is, within 30 days of the item's last estimated date for delivery, opening a case for item not received gives the seller 3 days to refund you, or if they enter a tracking number showing delivery, this will close the case in their favour, and they will not have to refund you.
If the 3 days lapse with no tracking number entered, and no refund, you must escalate the case and eBay step in and force the refund. It's timed to the second from opening the case, exactly 3 x 24 hour periods need to pass.
@alsm_741145