A few things....
First, 1 is a small value, and 6 is not very often. So just at least for testing you might want to use some extreme values to make sure it's working. I'd put it in the step event, and I'd move the view like 10-20 pixels.
Secondly, I'd move it based on the starting position, not the current position, otherwise your view will "drift and jitter" instead of shake.
ie...
view_xview(0)=current_xview+random_range(-20,20);
Thirdly, if you have any other object somewhere setting the view, make sure it's off, or make sure you are setting your quake effect to run afterwards, for instance putting this in the end step event.