Save File wont load

@maiaburton  Please check manually for any older saves, as described in the guide.  It's possible you have one or more but the game isn't reading them for some reason.

However, if you used "save as," you would have created a new save slot, so to speak, and that wouldn't have backups unless you'd saved it more than once.  For example, if the save file itself (as in, the label it has in the saves folder, not what you named it) used to be Slot_00000004.save, and you used "save as," the new save file created would be Slot_00000005.save, with no older versions of Slot 5.  You could just use one of the Slot 4 saves though.

If you can't find a save to revert to, try loading the current nonworking version, except choose a different household to play.  If it works, play that household for a few sim-hours, use "save as" to rename the save (so your original remains intact), quit, reload, and see whether you can go back to your main household.  Let me know how it goes.