My RB boy, Mr. Kitty, used to do this whenever we moved. I was in college when we got him, so we moved around a little more than we do now. We had him for 10 yrs ( he was 2 or 3 when he first came to us). As soon as we would get to our new place (mom's house, new apt., etc...), he would immediately go into hiding. Usually under a bed, or the couch. When he was younger he would do it for about a week or two, only coming out for food or to go potty. I think sometimes he just need to get his bearings, and feel his way around his new place. He was an extremely active and well adjusted cat, he just need a little extra time to get adjusted! So please don't give up on your kitty. Just and let him know that he is safe and loved, and before you know it he will be out and about!!