Symptom
If you have a multiple plate size greater than sum of single plate sizes + Grid Cutout Amount with 2 or more plates consumed in the master material, you can not select GRID CUT OUT from the PLATE menu in XGW..
Cause
You may also determine through the course of testing that if you switch from table type 9 (laser) to 1 / 11 (rotary) that the grid function becomes enabled.
Workaround / Resolution
Assuming that you are not violating any rules of grid cut out (size of sums of single plates + Grid Cut Out amount are less than or equal to the size of the master sheet), chances are your origin is set to CENTER and this is not possible in this configuration. Adjust the orientation accordingly (top / left) and you will notice that the grid menu option becomes enabled.