You can still file a successful claim and receive a refund WITHOUT a rejection letter from a TPA. You just tell ebay you have reason to believe the item is not genuine. I’ve had to do this before. I don’t think ebay will make it difficult, in particular since the item did not come with an LOA from an accepted TPA.
Not likely to be genuine: Our authenticators believe that the item, if physically submitted to P.A.A.S. for examination, would likely not receive our certificate of authenticity.