To check the current permissions and owner/group of the serial device:
ls -la /dev/ttyUSB0 # check the USB port
crw-rw----. 1 root dialout 188, 0 Apr 3 21:16 /dev/ttyUSB0
id glenn # check user is in the dialout group
sudo usermod -a -G dialout glenn # add the dialout group to the user
sudo groupadd mynewgroup # adds a new group to the system if required
If you had to add the dialout group to the user,
you will need to log out then log back in and now you should have access to the device.