Gaussian blur doesn't effect my objects in "Ray-traced 3D"-rendering

I'm doing a 3D-text in the "Ray-traced 3D"-rendering. When I duplicate the text, turn it 90 degrees and add the "gaussian blur"-effect to make a shadow, the gaussian blur doen't show any effect at, no matter how high I turn it up. The gaussian blur works for non 3d-objects and "Classic 3d"-rendering though. What am I doing wrong here? I've seen others to the exact same thing on tutorials and it works for them!