Unfortunately buying SDHC cards from Ebay is among the most risky businesses possible. The vast majority of cards sold there are simply fakes, in the sense that they sell off small-sized cards as large SDHC cards.

The advice to everyone is to stay away from SDHC cards sold via Ebay.

Note, though, that very old SD readers won't be able to handle SDHC. In general you should also not have to format a new card, it's pre-formatted and ready for use. I've never ever reformatted a new card and I haven't had any trouble.