Most probably the tech update is using the same data storage (AppData\Roaming\RenPy) folder as the pre-tech update, so it's blocking going back to the old version. Deleting the game folder from "AppData\Roaming\RenPy" should let the old version work again.Does the new tech update break the old version? Tried to go back to the older version and can't get it to work for some reason.
Back up any save files before you delete the game folder from "AppData\Roaming\RenPy", otherwise you'll have to start from the beginning of the game.