If 30 days have lapsed there's nothing you can enforce the seller through eBay, to offer a refund. eBay has a 30 day MBG policy, so you need to claim within 30 days of the item's last estimated date for delivery.
If you have received this notification after this period and within 120 days of purchase, you could try your payment provider for help with a refund, or to start a chargeback.
Was this purchased from a registered UK business seller, who is now not replying to your request for a refund, you can if you wish contact Citizens Advice if you wish to pursue this further.
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