What does the tracking, if any, indicate?
If there is no tracking or it does not show progress in your direction, you can file an "item not received" case with eBay the day after the last estimated delivery date shown in your Purchase History.
https://www.ebay.com/help/buying/returns-items-not-received-refunds-buyers/get-help-item-hasnt-arriv...
If the seller does not cooperate, after three business days you should be able to ask eBay to step in and refund you.
If tracking shows delivery but you do not receive anything, check with the shipping service to determine if the tracking number corresponds to a delivery to your address.
If not, you may be the victim of a false tracking scam or the seller may have given you the wrong tracking number by mistake. Either way, see here for some good instructions about what you can do about it:
https://community.ebay.com/t5/Shipping/What-do-you-do-when-ebay-support-will-not-help-you/m-p/340803...
What kind of feedback for selling does your seller have? You can avoid many issues by choosing to only do business with sellers that have a proven track record of delivering what was sold and that have sold similar sorts of items before. Avoid new or unproven sellers, sellers with a pattern of serious negative feedback, or sellers that have drastically changed behavior or that have unexplained gaps in selling feedback.
If your seller is a drop-shipper, the seller may have been the victim of the company doing the drop-shipping and providing the tracking number.
