As you can see in the attached sample model, as soon as I put a time other than 0 in the Gripper Action Open Time field, then the clamp never moves. It does not open or close.
But if I leave 0 in the Open time field, then the gripper will close according to the Close Time field and open instantly in 0 time.
So there seems to be a bug when we put a value greater than 0 in Open Time field.