I know this has been asked before so a search might yield a better explanation of how to handle...but essentially;

the tickets you have already booked while a platinum continue to have your old status attached unless manually "refreshed" by a ticketing agent.

The general recommendation iirc is to call and have the desk "refresh" your ticket manually beforehand aka now to ensure your ticket reflects your current EXP status and not the original PLAT status from when it was booked.

I hope this helps.