Allegedly, on or about 30 October 2017, tar@sonic.net sent:
The address "liberty.local:631" is suspect, as the server should be liberty.localdomain, but even adding liberty.local to /etc/hosts made no difference.
..localdomain versus .local sounds like an Avahi/ZeroConf issue to me (the issue being more name resolution than CUPS configuration).
How the system resolves hostnames differs for Avahi than other traditional networking. You need to have the Avahi service running, and access to their ports (different from normal DNS ports).