Circuit works when I touch the mass, please help me

Hi, could you help me with this circuit, actually I don't know why the led (D1) is just on when my hand touches the mass assume that I connect P1.6 to P1.1 and the switch lets the current pass through.
The problem is not in led, switch nor R because the led is on when I connect the first pin at switch and the last pin at R to a 5V source.

Please help me,

Thanks!

what mass?

Oh sorry, I actually mean Ground, I'm so sorry, "mass" is in french :)
In my circuit, ground is covered around lines and devices

As far as I've undestood, you connect P1.1 and P1.6 with a wire, then close the first switch S1 (1-8) but D1 is off unless you touch the ground with your hand. When you leave the hand the led goes off again. Is it correct ?
Do all the leds having the same behaviour of D1 ?

From the schematic diagram I don't see anything strange.

It could be something related to the PCB construction.

Yeah, I think the problem is at the PCB construction, but whatever it is, I can hardly explain why when I touches my hand to to ground, the circuit works.
I mean it is still a vague unanswerable question.

If you have not only to touch, but to press a little bit, it could be is a problem related to the soldering of some component.

I am not following you. Unless you connect some other circuit to multipin connector P1...NONE of the leds will ever light up. Explain what goes on on the other side of P1.
It might be oscillating