Refused return?

So as a seller I'm entirely confused as to why, as a customer I was completely refused a refund last week when the product was faulty.. Is this a new thing? I bought a pre workout powder, it was clumped up like it had been exposed to moisture in the air, totally unusable. Now being a seller I wouldn't refund unless the product was entirely unusable. I was shocked when I attempted to return the day after receiving the item only to be told this item is not eligible for refund.

Are there products which can not be refunded?

is this new?