I don't know the scientific reason, but I was able to see the 3D image roughly around 5% of the times I tried. And after having success in seeing one, I was not

I don't know the scientific reason, but I was able to see the 3D image roughly around 5% of the times I tried. And after having success in seeing one, I was not able to learn how to do it always. The 5% success rate remained