Vinted complaint: Accusing me of selling inauthentic item

I recently advertised a children’s Givenchy tracksuit to sell on Vinted. I bought this for my son a few years ago from kids cavern which sells high end designer kids clothes. My listing was hidden and I was told they believe it was not authentic, anyway I sent more pictures of labels, stitching etc and then was told it was fake and to stop selling these items. However, I wished to argue my case and fight this as I know where this tracksuit came from and how much I paid. I asked for the matter to be taken further to be shut down again and told the decision was final and to stop selling it. I have challenged this again asking for their reasoning (which I haven’t been given) this is not acceptable to accuse someone of selling fake goods and then not even explaining why? As I said this came from kids cavern so I don’t see how it can be counterfeit (unless kids cavern were selling inauthentic clothes which I highly doubt) but when I ask for the matter to be looked into further or who I complain to I am shut down! Now I am willing to fight this as I know they are wrong surely this is not allowed? I have asked them to involve trading standards and give me their reasoning I don’t think this is acceptable from Vinted to make accusations and then not back them up and then completely shut me down and not let me fight my case