If t was tracked as delivered on time, surely eBay can see from the tracking record? If so, it might be worth trying again.
DPD's "next day" delivery is probably a perfectly good service, but the title is almost guaranteed to create disappointed buyers. Perhaps we're all getting too used to Amazon, where next day really means the next day!
On eBay, "next day" seldom means that the buyer will receive it the next day. At best they can hope to receive it the day after the seller has dispatched it - assuming that DPD receives it before the daily cut-off time. Even then, 24 hour delivery isn't guaranteed. A less explicit title lilke express or rapid woud be avoid raising false hopes.