Hello guys thank you very much for taking time to answer me.
@jayeff : ''1. Try using a different USB cable or connecting to a different USB port on your PC or even try on a USB port on a different computer. (This eliminates the USB cable, your computer's USB port(s) or your computer as a possible cause of the problem)''
==> I have tried another USB cable + block to charge my phone and I am facing the same problem : it is only working when phone is OFF
"2. Inspect the USB port in the phone using a strong light and a magnifying glass.
a). Check that all 5 pins are there, especially the middle pins and that they are all straight and parallel with each other. (pins 2 & 3 are the data pins, 1 & 5 are the power pins, pin 4 is the 'sense' pin for use with OTG etc.)"
==> 5 pins are here and all straigth and parallel.
"b). Check that there is no lint or dust in the port enclosure. If there is use a vacuum cleaner with short sharp bursts to try and remove the lint or dust. If it is stubborn, try gently using a wooden toothpick to dislodge the debris. DO NOT use a metal probe and try not to damage the pins."
==> only at the entrance of the USB port it looks a bit like rust (because of the color) but on a very small part and not that close to the pins. Otherwise, nothing, everything is clean
"3. The USB port could be loose on the systemboard. "
==> I tried but nothing. And when it is a lil unplugged (like not very well plugged so you can have some ON/OFF charge), it is still only working when phone is OFF.
BTW Thank you very much for trying solving my problem.
@virgil Hey ! I am totally newbie for this kind of stuff. I did find the ADB Control for Root Users but what is Fastboot ?
Best regards
Nicola