Post deliveries are on a real slow down because of the Christmas loads, and some items are not sent tracked.
However, tracking aside, if the seller is being unhelpful, and if a reasonable time passes your item's last estimated date for delivery, and you have not received the item, go right of the item purchased, and from More Actions select.... I Have Not Received My Item.
If you are not fully refunded within 3 days, you must escalate the case on day 4 or within 30 days from opening the case, and eBay will step in and force the refund.
Do not close the case early for any excuse or promise the seller may give, and do not forget to escalate.
@jenny-5189