No sims?

I first noticed that when I came with my sim to work (doctor) there was only one patient and when I sent him home no one else appeared. Then I went to someone’s house and knocked on the door, ”nobody’s home” popped up in the corner even though it said they were home. I went to several other peoples houses after that and the same thing happened. I also went to several public places and they were empty, not even any employees. When I try to invite people over it says they’re coming but then they never show up. No one’s walking around the neighbourhood either. The only mod I have installed right now is mc command center. What’s going on and how do I fix it?