Go to your Purchase History, find the item, and under “More actions” click on “Return item” and select the reason for the return. “defective". Attach a photo.
The seller will have 3 business days to either accept the return and provide a prepaid return shipping label OR refund without having you return the item.
If they don't do either, you can go back to your Return Request details 4 business days after you filed the Request and ask Ebay to step in.