Knox won't come in house once moved in

I have a similar problem. When I ask Knox to move in, it takes me to the merge households screen, I move Knox to my home (his mothers don't appear in his household) and I hit the green "done" check mark. Then nothing happens. I can't click out of the screen. I have to end the program through task manager, even though it doesn't say it's not responding. Tried it twice!