My sims have all gone!

Hi, this is a really weird one but I updated my game today and when I've gone on to play it all my sims have gone invisible.

The portraits are showing as if they're on another lot but if you hover over them it says that they are at home. I've tried to reset them but it just says the sims are not found. This is happening with all my sims on different saved games.

Does anyone know what this is?