Hi Kevin,
Thanks for the suggestion. Yes, creating a new extension and then forwarding all calls to the Special Menu 999 extension worked. However, I'm still curious why we needed a workaround - why did the original option disappear? The world may never know.
Our self-hosted 3CX install was working fine for a few years, until our trunk provider, Wiretap asked us to migrate our existing trunks to a new version. I tried updating the trunk hostname per Wiretap's instructions, but in the 3CX portal there was no place to update the hostname, so Wiretap...