The only way to zero the machine coordinates is to home the machine.someone posted i should move the spindle, ref all zero, click machine coord[red box] and zero each axis. that doesn't work.
If you click Ref All Home, and then the Machine Coordinates button, all the DRO's should read zero. IF they don't, then go to Config > Homing/Limits and make sure all the axis are set to Auto Zero.