And the answer is that INADYN in RC1 of TrueNAS Core, is version 2.2.
Updating INADYN to v2.7 fixed the issue.

The Dynamic DNS Feature is using INADYN utility to keep my public ip address in sync with DNS-O-Matic.

Seems to work well with the first run.

The second run generates this cryptic error:
“Failed to get IP address for default@dnsomatic.com”

Now, that should be fixed under TrueNAS Bug Ticket NAS-103353.

Not for me (or do I have a different issue?)

Things to check out:

File locations
inadyn.conf – /usr/local/etc
log file – /var/log/