Telnet to the Digi device/terminal server and login as root. Change the "dev" setting to "prn"
#> set port range= dev=prn
A reboot of the Digi unit should be done when changing this setting:
#> boot action=reset
Also, another process may be on the port in question
Type 'who' command at the command line of the Digi terminal server
If output shows process on a port you are troubleshooting type
#> kill tty_number (look for tty number in the first column