The central pin should connect to output, not ground. Ground should connect to pin 1 and 5V to pin 6.
Well.
Actually, you should see about 3.0 to 4.2 V on pin 6, if you’ve wired it the way it’s shown. That’s because the way it’s shown is wrong. I believe that’s the way Sam built it, and it works for him, but it won’t give you 5 V at that pin. The problem is that the regulator is connected to VIN on the Arduino and it should not be; it should connect to 5V.
Anyway, whether you have 4V or 5V on rotary pin 6 you should have 4/5, 3/5, 2/5, and 1/5 of that on the other pins. If you don’t then either the switch is broken or you have bad connections to the resistors. If you don’t have any of the above voltages check the resistor between pins 6 and 5; if you have 4/5 but not 3/5 check the resistor between pins 4 and 5; and so on.