Machine motion was prevented by a physical obstruction. Typically, this happens as a result of attempting to drive beyond the physical limits of one or more axes.
As a result, the machine is placed in Manual mode.
What you should do:
Determine the cause of the problem.
Remove the physical obstruction or correct the measurement routine.
If the problem persists when the machine motion is not obviously restricted:
You should contact your Giddings & Lewis service representative.