A few questions..
Who is the carrier and what are the first 3 letters or numbers of the tracking number?
Where is the item being sent from?
What is the estimated delivery date?
If it is after that date and less than 30 days have passed since that date, you can open an item not received claim. The email that you received when you made the purchase should have a link to open an item not received claim. Make sure that you are signed out of your current eBay ID.