Warning The repository is archived. Try to use https://github.com/HGStyle/GD-SaveFileFixer instead if my program doesn't work for you.
This tool can fix most problems caused unable to open the game by the savefiles. (which is the game will only launch if you move the savefiles to other folders)
You need to install at least Python 3.6 to run this program.
Or just download the release for Windows (requires at least Windows 7 with Service Pack 1) so you don't need to install Python.