Can't connect printer to repetier-server on RPI3 I'm struggling to connect a K8200 printer to a rpi3 running repetier-server 0.86.2 armhf.

Everything works fine on a PC with the 0.86.2 windows version, but on the Rpi i'm stuck on the second step of the printer setup : 

I define my firmware, Marlin, my baudRate at 250000, then I tried every port that seems involved (/dev/serial/by-id/usb-FTDI_FT231X_USB_UART_DA00DDXD-if00-port0, /dev/serial/by-path/platform-3f980000.usb-usb-0:1.2:1.0-port0, /dev/tty/USB0, /dev/tty/AMA0, )
but whatever I may try, I'm stuck on "En attente de connexion", that forbids me to go to step 3, as to see my printer connected.

I tried to use the reset button on the printer board, as unplugging-plugging the USB, with no more luck.
/var/lib/Repetier-Server/logs/server.log don't shown any error.

Note : CartesianVirtual port still works fine...

What else can I do ? Is there other relevant logs anywhere ?

I'm unsure if this question should have been adressed to rpi, 3d printing or linux community, I'm sorry if I offend anyone :)
Thanks to the repetier team on git hub, we found that the problem came from a permission issue on /dev/ttyUSB0, as the user repetierserver couldn't access it.

Other people reported that these commands solves the problem:
sudo adduser repetierserver dialout
sudo adduser repetierserver tty
but in my case it seems I need to run :
sudo chmod 777 /dev/ttyUSB0
in order to solve this.