I mean from what I'm aware it's not exactly possible unless you have an old version save file which is incompatible, imported to a newer game version. You could try uninstalling/deleting the entire game folder (save the save folder if you have any progress from previous versions) and try to do that again. Other people had an issue with incompatible saves and really there was no other option than to start fresh. Though from the current lack of content, I wouldn't be that mad restarting the whole game.
TLDR: try to delete the game folder or just the saves folder and start fresh
If that doesn't work then I think the dev need to handle it though unfortunately he's not very active in the comment section. Maybe try to explain your situation further if you want some help.