Hello, this is quite strange. It may have to do with the game being updated to the latest version and you can't load a save game from the previous version of the game. If this is not the case, it is most likely a bug in the game engine when this save game was saved.
The simplest solution is to load a previous game, but you can also access the hacker menu and load the chapter you went through in the story (although many of the decisions you made will not be taken into account in the latter mode).
Don't hesitate to ask me any questions you have about this.