Cannot Move Sims In

I am no longer able to move sims into my town. I invited Flipper to live in my town and when I go to move him in nothing happens. I’ve tried inviting other people and when I invite them they say they’ll wait for me to move them in, but when I speak to them again it’s like they never agreed to move in. It only suggests Flipper to move him in and it won’t let me move him in. I select his name and then the dialogue box goes away and nothing happens. The building screen doesn’t appear or anything.