The global save file is missing / got recreated as a blank. Could you describe how old your saves were, what you did before that etc?
Did you perhaps try migrating your save folder without copying that?
To work around your issue at hand:
- Make a backup of your save folder
- Save in a save slot you want to later load from
- Copy&Paste the fitting save from your back up save folder into the game's save folder
It will initially show you the wrong meta information but if you then load from that save, it will load save you copy&pasted over.