motor sheild

I have an Arduino UNO, mounted to it I have a seeed motor shield (1.2) and connected to the motor sheild is a mercury stepper motor # SM42BYG011-25. I have a DC supply connected to the motor shield, and the motor connected to M-, M+, - M-, M+.
I am running the sample code " stepper-onestepatatime" from Arduino . Nothing moves, I feel some hold on the motor shaft but it will not turn. any Ideas or am I not wiring it correctly?