Once in the vines tunnels go straight in it ,don't take any turns, and at the end you will find the room with the valve, you need to inspect to find it, it's in the upper left corner of the room.
Maybe in the future, anyway you can update your version using the PC ones, like I did.
Download and unzip it, take the game folder and drag and drop it inside the Resources folder of your game.
The path to do so is: Right click on your game icon and choose Show Package Contents from the pop up menu/Contents/Resources.
Delete or drag out of the Resources folder the old game folder before putting inside the new one.