Getting ntpd to work on a toy OpenBSD 6.3
You need to set an interface for it to listen in /etc/ntpd.conf and you need to comment out the constraint on Google, because afaict OpenBSD does not trust one of the certs there. For more serious use you should tackle the root cause of the cert problem instead of course.
openbsd dev - bugs - ntpd with default config broken in -current