Apparently AuthenticateFirst does not have the expertise to authenticate every product out there. This company has TWICE made an error on David Yurman jewelry pieces, not having the requisite knowledge about David Yurman stand alone store items and the AUTHENTIC but slightly different items DY makes for retail outlets (like Saks and Nordstrom) so as not to be competing with them directly AND the items they manufacture for specialty causes or groups. So... they are NOT the be-all, know-all of every item out there. Yes, I took both my items directly to a huge DY retail store where an experienced older gentleman explained all the iterations of the DY manufacturing plants and some of the items they scale down for affordability (smaller stones, lesser mm sterling cuffs, etc.) He was particularly nice to me and was taken aback that someone would deny the authenticity of clearly authentic items.
BOTTOM LINE HERE: AuthenticateFirst may or may not be a legitimate company but they CLEARLY don't know everything about everything.
SELLERS should avoid Tradesy because they have apparently been drinking the kool-aid. But they will not change their mind on anything even if you have proof of authenticity. My guess is there is some collusion (kickbacks?) between Tradesy and AuthenticateFirst.