I am also having this problem now. My game was running fun as of yesterday, today I cannot load any of my saved game files either. Super annoying. Thought it was my mods but it's actually the game itself.
@Supermatthea Sorry for just replying now! Try this [ https://www.carls-sims-4-guide.com/help/save.php ] it basically tells you what I also did but I couldn't find the actual website I followed. You have to copy your game files into another folder, so even if reinstalling does something to your saves, you'll have the backup in another folder. I'm just not so sure it works the same for mac and pc, as I did it on a pc but it's worth trying out if you're worried about loosing something. Hope this helps!
Today's patch (184.108.40.2060) should help with this issue.
If you're still seeing this problem after updating, please let us know.