but your drawing has com and NO pin connected and mine is NC and COM pin on mini limit switches...
check my pic of 2 switches for one axis in series connected and tell me if I have wired it correctly???Click image for larger version.
Where does it say that John shows com and NO? Do you have a multi meter? I suggest you read the post again. As the drawing clearly shows you the way it is wired.
With a multi meter is is very easy to check you have it OK. You can also check if the two grounds ie the 5V one and the one you referred to are indeed connected together. If you are not sure use the 5v ground