Before you open a Paypal dispute which you could more easily lose, go to the link below and scroll to the bottom and use the "contact us" option then ask to speak to a representative and explain what has happened with the seller getting you to close the case, and see if they'll reopen it for you.

https://www.ebay.com.au/help/buying/returns-refunds/get-help-item-hasnt-arrived?id=4042