It may just be me, but I would never buy from anyone not even NERD itself, if they said no refunds.
I think you may have gotten scammed my dear.
Follow the advise you have received. Be polite, ask what the exact issue is, ask how many times the baby has eaten so far and what it has eaten. Don't leave room for a three word response.
If you do not receive a satisfactory answer within a day or two, file a claim with PayPal, since you already know the buyer won't give you a refund.
Gale