I can't feel the microcurrent on my LED Comb?

Firstly, let me reassure you that this is not unusual. Maysama’s LED Hair Growth Comb is set-up within our factory to the following microcurrent pulse outputs, 

Level 1 - 780V

Level 2 - 1.04KV

Level 3 - 1.32KV

Level 4 - 1.68KV

Whilst the deviation from this specification is calibrated to within +/- 10%, the level of sensation varies greatly between individuals. Most consumers are unable to feel microcurrent on their scalp due to limited nerve endings in this region. The degree of sensation is generally increased when using a hair serum, which increases conductivity, but for most areas of the scalp it is normal for the degree of sensation to be negligible.

For further confidence, you may wish to hold the comb on the palm of your hand (slightly damp), where you should feel a slight tingling sensation, demonstrating the efficacy of the microcurrent. 

I hope this provides you with reassurance that, if the LED lights on your comb handle are illuminated, the microcurrent setting is indeed working.