Step pins are getting a pulse so unless you are sending a fast pulse you will hardly see them flicker. If you change the active state of them then they will be lit and slightly dim as you jog. But likely you will have to jog after the change before they will change state.
Hood

But shouldn't the step pins have changed even if randomly?

You will need much faster measuring equipment than you are currently using if you want to see much activity on the step pins (oscilloscope would be good).

Seems you are trying to find a fault where none exists 

Tweakie.