On the listing, it should say the approximate processing time for shipment. Keep in mind, those are business days. Most seller don't ship, or even package their items on the weekend.
If it has been longer then the given time frame, kindly message the seller asking on the status of the shipment. Most ebay sellers on here are individuals or small businesses, as opposed to large corporations. It is possible for the one person to get sick, or not have transportation for the day.