Zenified™ uses electrical impulses to give you the same benefits as acupuncture, which is a time tested pain relief technique. To see the full benefits of Zenified™, check out the product page https://zenified.co/products/zenified
The pen is a monopole current output, so the other pole current should be conducted by hands and form circumfluence with the nid of the Electronic Acupuncture Pen. so that it will produce electrical pulses. So it is normal to feel a little numbness of the holding hand, it is how the meridian pen works, not quality problem.
If you don't feel anything, that's probably because you are not stimulating the meridian points properly. In the user manual there are illustrations that explain you how to stimulate those sensitive points properly. If you still think the stimulus is too light, try to gradually increase the power and see how it feels.