My dining window is open for the first couple days in January, and for some restaurants (e.g., Cinderella's Table and Biergarten, plus a bunch of others), the website won't even let me choose those dates - they show up as being within my window, but the numbers are grayed out. But I can book other restaurants for those days. Have they just not released those restaurants yet? I've never had this problem before!
Disney dining has no idea why there not loaded into the system nor can they book them through their system.