Do you back your Paypal account with a credit card?
Because that's the only way you are likely to ever see a refund.
And even that is unlikely.
EBay offers Buyer Protection for up to 30 days after expected delivery date. So four months out, you are well past their deadline.
Paypal offers Buyer Protection for 180 days after purchase. Again, past their deadline.
If you do back your PP with a card, go to the 1-800 number on the back, with all your dates, payment amounts, currency info, and transaction numbers, including the tracking number on the returned package, and ask about a chargeback.
Keep in mind that cards have deadlines too, and four months is pushing it, although some cards allow up to six months.
So what you have here is a learning experience.
We've discussed deadlines for complaints.
Another point, you MUST return items using a tracked/Delivery Confirmed service, or you cannot prove that the seller did not receive the item.
was going to leave feedback and didn't because seller asked me not to -- That's a red flag. You only have 60 days from purchase to leave feedback. Such a request is a signal to go to a Dispute.
More important.
Unless the seller is either the manufacturer or a designated retailer for the manufacturer, the warranty is basically worthless.
For example, if you bought a toaster from Canadian Tire, they might replace it or give you store credit, but they would be returning it to the manufacturer for credit themselves.
The manufacturer offers the warranty, not the retailer , in most cases.
Manufacturers don't honour warranties on sales from online sellers, because the item may not be what they sent out.
That is, a lot of eBay sellers are buying deadstocks, returns, or refurbished goods.
To say nothing of the outright crooks selling stolen or counterfeit items.
And don't buy batteries from China. It will not end well.
