2 in 1 extruder one side only goes back and forth rapidly and will not extrude.

We are troubleshooting the 2 in 1 extruder in a gmax pro. the #1 motor doesn't turn. it just ticks. When we move that cable to the #2 motor it does the same thing. Not sure how to trouble shoot the main board. We have tried different cables with no change in symptoms? perhaps a driver issue. since both motors will run on the motor 2 cable? Any help would be appreciated!!