Cannot see, visit, or invite any NPCs at all

Hello,

I'm having the exact same issues as this post. In short, when I invite people over, they say they're coming over, and then never appear. When I visit other houses, there's no one there, even though there should be. And when I try to take control of those NPCs, it says they're in a "Secret" location. I've tried all the steps they have, and it hasn't worked.

I then tried to follow the troubleshooting steps, and in the new game, there was no more error. As soon as I put the saves back in, however, the error exists once more. 

I have Sims 4 and Get Back to Work and MCCC. 

How do I fix this?