I think the park reservation system has been doing some wonky stuff. I made my park reservations months ago when I purchased my hotel/ticket package, but about 2 weeks ago I got an email telling me to "make my park reservations" and when I went into the app, they were all mixed up, and some were missing altogether. So I started re-reserving them, only to get a "you've run out of valid ticket media" message. I walked away to deal with a work issue, and when I re-logged in, all of my park reservations were showing correctly.
So, maybe give it a couple of hours? At the end of the day, they won't "charge" you for a used ticket day unless you show up at a turnstile, so as long as you show a reservation for the days you plan on being in the park, you should be fine.