If the seller does not respond within 3 days of a case being opened either with a refund or with tracking showing delivery, then you Must escalate the case, ask eBay to step in, and they'll force the refund.
If you didn't do this, then through inactivity, the case will close, and you cannot open another case for this item with eBay.
Never forget to escalate.
Now, you'll need to turn to your payment provider for help with your refund.
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