Saves not reading in game

layniiiiii  To be clear, you're saying that when you try to load one of these saves, the game puts you in CAS to create a new sim, rather than loading a household?  What about a backup copy of one of these saves?  Here's how to recover it manually:

https://sims4.crinrict.com/eng/2014/09/recover-backup-save-game/

Please also let me know whether you're currently using mods, or were using them and are not anymore.  Some mods have been causing sims to disappear even after the mods are removed.

Yup, it puts me into CAS to create a household to start a new save. I have a backup folder I've already tried to copy in, and it hasn't been working.

The only mod I use is MC Command Center.

layniiiiii  Just to make sure this problem is limited to your old saves, please create a new save, play for a bit, save your progress, quit, restart your computer, and see whether that save loads.

Please also make sure all your owned packs are loading.  You can filter by pack in CAS or Build/Buy to find out.

I started a new save when I noticed the issue and played for a bit. I just popped back in and it's still working -- all my packs are loading, it's just my old saves for some reason.

layniiiiii  If you create new sims in one of the saves, and place them in the world, can you find your old sims either in their houses or in Manage Households?  If so, can you play them?

If you can play an older household, let the game clock run for a bit and use "save as" to rename the save.  Quit, restart your computer, try to load the save again, and let me know what happens.

If you can't play an older household, but you see them somewhere in-game, try saving them to the library and see whether they place in a new save.  Quit and reload the game in between steps.

hi, so sorry it's been six months -- I hvaen't been playing the sims. I tried to open up those old saves that weren't reading but they just opened into my newest save file.

layniiiiii​  If you can't see any of the saves at all in-game, even the backups, then there's really nothing else to do here, unfortunately.  It sounds like something corrupted the saves, but it's hard to say what, and it doesn't really matter if the saves aren't viable anymore.

I know it doesn't help now, but in the future, it's best to keep your own backups whenever possible, not just the game's backups but your own files preserved at different points in time.  And maybe you'd want to periodically save your sims to your library so you could place them in a new save if it came to that.