Sounds like it should work provided the base of the transistor is being driven high by the BOB (break out board ? Sorry, I'm new to this site having just purchased a mill to convert). The BD679 is a darlington device so won't need much base current to switch it on.

It sounds like the transistor is missing its base drive - perhaps you need to configure something in your CNC software to make Pin 14 a suitable output ?

HTH

Cheers
Robin