A FlyerTalk Posting Legend
Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,417
I assume that you successfully activated the new card first? Sometimes I've been asked to get on the phone with an AmEx rep to convince them that it's me when I either have a newly renewed card or when my spending pattern looks unusual for me or looks like it might be a case of fraud. I've also experienced apparent declines when the merchant or website didn't process the transaction correctly; in those cases, usually AmEx doesn't even see an attempt to use the card.
Nevertheless, IMO it's not wise to use a new Plat card for MS or in a way that could be viewed as irresponsible, especially if your application wasn't a straightforward case of regular salary income that can be easily verified.