A psi ball is simply an exercise in energy manipulation. If you are not "aware" enough to sense energy, you will not sense/see the psi ball forming. Understanding and awareness are now, and always will be, more important than your ability to make such a thing.
I agree with Awake, and I would suggest keep trying. Just because you do not sense the psi ball does not mean you are not making one. However I have read somewhere, not sure where, but by practicing making a psi ball and attempting to sense it, you are therefore helping your senses out (like exercising a muscle).