Not sure how long you held your platinum for, but Platinum Concierge is no longer what it used to be, massively reduced in scope. In 2017/18 I managed to get several sought after, fairly last minute, restaurant bookings whilst travelling in the USA. Now this is officially something they no longer do as they have acquired the Resy booking platform and they will point you in that direction. Unfortunately the restaurants on Resy are an “odd” list as most sought after ones will be on either OpenTable or Sevenrooms reservation systems, and Resy does not integrate with them (as it should be effectively a competitor).

Trip booking (flights and hotels) is effectively managed by Amex Travel /Expedia, maybe a dedicated team within the larger team, but it is no longer a centralised Concierge team that would handle al request as it used to be.

As a matter of fact, the “all you may want to ask for” concierge service has quietly disappeared from recent marketing materials for the Platinum whilst before it was one of the prominent advertised benefit (like NatWest/RBS Premier Black still do for example).

so in short, your expectation of the concierge service needs to be lowered as, in my opinion, it is actually no longer a feature/benefit of the card (rather a travel agent service linked to selling other products within their business).