I;ve not recieved my items from seller

Question

Hi I recently won a bid for an item on e-bay my first time bidding! The seller said it would be shipped within 2-3 days, it has now been over a week and a half and I still have not recieved the item. I purchased postal insurance too. I e-mailed the seller and she said whe would track the item, but have heard nothing from her since, I have e-mailed her again but no reply, who do I contact about this?

Any help greatfully recieved.