The booking window for dining reservations begins at 6 am EST (sometimes at 5:45 but not guaranteed). Unless you're in a different time zone where it is 7 am for you.
East Coast I had no idea it started at 5:45. Ugh. I was able to get a dinner reservation for the day we are scheduled there. I prefer a lunch one. I will keep trying!
OP Update--got Sci-Fi for our 60+2 at the time we wanted! I was so excited this morning
Also got Space restaurant for around an hour earlier than preferred, and could have gotten Storybook but we decided against that after DDs looking at the menu
Ive still not seen a single Space reservation for our 6 day trip but easily found a bunch of Sci Fi ones even a week and a half after they opened. I ended up booking it when I read about the new menu.