Stepper Motor Trouble

[Bethan]

Hello,

Looking for some help with a rather unusual problem - I'm using fairly large stepper motors, but can't currently get them to work.
The motors I'm using are on this page:
https://www.oyostepper.es/goods-88-Moto ... ables.html

I've wired the motors in a bipolar parallel configuration according to the diagram. I'm using A1 as positive, A2 as negative, and B similar. When I start to home the unit, the motors will jerk a bit as if they're about to move, but then stop. I can move them manually afterwards, so I know they're not idling. I plug them into the extruder driver, and I notice the same behavior - but it will just jerk a bit and refuse to move (only on my first try, after that it won't move until I reset the unit).