Cannot open /dev/ttyS0: Permission denied

I’m trying to implement serial calculation between a Jetson Nano and Mitsubishi PLC. An RS422 to USB converter cable is used for serial communication(USB is connected to Nano).

I first added the Nano to dialout group as suggested by many users. When I run the “groups”, the output displays dialout. Despite being a member of the dialout and tty groups, I still can’t access the serial ports.

Can anyone suggest a solution for this? Thanks in advance.

What do you see for “ls -l /dev/<ttyWhichEverTTYItIs>”? Basically, who owns the tty you are trying to use?