Error using serial/fopen

Hi to all, Im trying to open serial port on matlab (on Linux Tumbleweed 64) and I check first:

1) Im in the dialout group

2)instrfind

3)chmod +777 /root/lock

and matlab keeps giving me "Error using serial/fopen (line 72)

Open failed: Port: /dev/ttyUSB0 is not available. No ports are available."

why?

Im writing code in app designer and don't know how to solve it in code.

Thanks