eBay's Money Back Guarantee works very well, but it has strict timelines  and actions, which must be followed to a T .

You have to open a case within 30 days of the item's last estimated date for delivery.

This gives the seller 3 days to refund you.

If they don't,  you Must escalate the case, day 4 is the earliest that option appears, eBay step in and force the refund.

Never close the case early on any thing the seller says or promises,  and never forget to escalate.

If the above is followed, you're guaranteed a refund.

@syzygy2104