The port is not connected.
This is usually a modem error message.
1. Make sure no other pieces of software are using the modem, if so, close
the applications, and possibly reboot the computer and try it again,
making sure those applications are still closed when the machine reboots.
2. If you just added an init string, or new drivers for the modem, remove
the init string, and rollback to the older modem drivers.
3. You could try uninstalling/reinstalling the modem.