The default tape device /dev/rmt/0, or possibly the device specified by the TAPE environment variable, is not currently connected to the system, is not configured, or its hardware symbolic link is broken.
List the files in the /dev/rmt directory to see which tape devices are currently configured. If none are configured, ensure that a tape device is correctly attached to the system, and reboot with the -r option to reconfigure devices.
If tape devices other than /dev/rmt/0 are configured, you could specify one of them after the -f option of tar(1).