Like the build manual says, set the temp, select the extruder0-gcode form the sd card. then NOTHING. the motor does not engage. I tested the motor and by moving it to the Y axis port on the Rumba. I can manually feed filament thru using the prepare, Y axis, 1mm movments. I move it all back to original locations. What am I doing wrong?? I follow the build manual calibration sections; but no success.