Hello,
I had a similaire issue.
When I launched the game today, after an update, I was asked to create a new avatar, was offered to do the tutorial again, and all previous save files were gone.
I started a new game and played for a while, and then exited the game.
Now, when I launch the game, my previous avatar is back again. I can load my previous save files, but not the new one I started today.
After investigating a bit, I found my old save files are in :
C:\Users\%username%\Documents\Humankind
Files created this morning are in :
C:\Users\%username%\Humankind
After the update today, I start the game and all my in progress games are gone. My avatar is gone. I didn't want to update, but I wasn't given the choice.