"Chi" is a very versatile term. In Martial Energetics, it is specifically defined as the sensation of flow and finesse. It is not a substance that can be measured, or an imaginary idea to be visualized, but rather a sensation that can be felt (as well as seen and heard). Much like electricity, chi can only be observed when it is flowing.
Chi is a principle that is only useful for guiding your practice if you are familiar with the sensation and proficient at generating it. So, what if you can't feel your chi? Don't worry about it. Just focus on the physical sensations that you can feel: force, momentum, kinetic energy. By honing your perception with the more gross forms of energy, you will eventually develop the sensitivity to detect the more subtle forms.
There is a saying that goes "First move the body to move the chi, then move the chi to move the body." What this means is that by moving the body under the influence of the Three Regulations and the Six Qualities, you will come to stimulate and detect the sensation of chi flow. Once you are able to attain this sensation reliably without movement, you can then use it to direct your movement, and hence be moving "under the influence" of chi.