I have a nervous Maine Coon. We just moved to a big house and she has been hiding for over a day now. She has not eaten or drank in a day. How long before I have to do something?
Can you shut her in a room for a while? A new house, especially a big one, is really scary and maybe if you made her "new space" smaller, she would be more inclined to eat and drink.
It's very common for kitties to not eat or use the litter box when in a new environment. My kitty was so stressed when we moved (5 yrs ago now) that she had fecal incontinence. If I was doing it over again, I'd confine her to a single room with litter box, food and water, a radio, comfy bedding, a feliway diffuser, and toys for a day or so just to get her settled and decrease her stress level. Then, I'd let her out while I was home to explore. I'd do this for a couple of days, then let her have free run of the house.