The probe changer control unit and the probe changer rack are not connected to one another.
What you should do:
Connect the probe changer control unit to the probe changer rack.
To clear the error, click Clear error in the XYZ Display window.
To clear it using an RCU-II, press and hold down the Servo Power Off button and then press the Joy button twice.
If the error reoccurs, contact your Giddings & Lewis service representative.