You've downloaded the latest release, which would be the public one
here (not sure if they've updated the OP or not with it, haven't checked)? Are you getting any sort of traceback or .txt file with an error? The other person that had a similar issue got their folders mixed up and was opening up the wrong one. Don't know if that's the issue here, but it's hard to help without any other signs.
You can delete Ren'py save in AppData. Windows Key + R > %AppData% > Ren'py > Find Game Folder > Delete Saves.