eBay complaint: REFUND

Good morning,
I purchased an item from vintag126060 (Omega Geneve 364435372638) Order number: 05-10465-26062 on Aug 26, 2023. The watch arrived on Tue, Sep 5, and after a brief examination I found that it had a missing part in the movement, and it was defective. I contacted the seller, who purposed a partial refund or a return. After I explained him the problem, he told me in a very unpolite way that I was the one who damaged the watch, and swore the watch was intact when he shipped it and proceeded to deny me any reimbursement or return.
Today, Sep 18, I went to my local watchmaker. After a brief inspection he ed my observations and told me that the rotor was forcely put in the place and the screw was indeed missing, and that the repair would set me on way more than 150$.
I am contacting eBay again to help me since you’ve stopped answering my e-mails.
As a buyer and seller myself on your platform, I find the seller’s attitude extremely rude and aggressive, and also a liar.
Despite the numerous calls for help, eBay is not doing anything to help me, only telling me to try to talk to the buyer and figure things out. The buyer wont answer me either.
I demand a full refund, with or without a return.
I won’t buy from eBay ever again and will give negative feedback everywhere I’m asked.