Do you mean that a message has appeared in the listing? Or that you personally have received a message? Who from?
Without this information we are only guessing, but if it's being sold elsewhere I don't know why you imagine this is with the support of eBay. EBay does not allow items to be offered for sale elsewhere while they are on sale here. The seller will suffer a range of penalties if you win it, but don't receive it because it's already sold.
In any event, be on your guard and if you win it, be sure to pay by a method that's eligible for eBay's money back guarantee, see: https://pages.ebay.co.uk/ebay-money-back-guarantee/
