VMA03 + NEMA23 = hums, it doesn`t work


can anybody help me please.
Is it possible to work with this combination ?

VMA03 Motorshield and Nema 23 stepper motor ( Nema 23 Bipolar 1.8deg 2.4Nm (340oz.in) 1.8A 4.95V 57x57x104mm 4 wires) =>

When i load this example == https://gist.github.com/Epsilon99/2757e52e06a7d2d50221#file-vma03-bipolar-stepper-driver == code the stepper motor only hums.
I use for the shiel an external power supply.
Can anybody help me please ???