NTP synchronization does not work when using FQDN of the NTP server instead of IP address.
Restarting the ntpd daemon manually resolves the issue:
[Expert@HostName]# tellpm process:ntpd
[Expert@HostName]# tellpm process:ntpd t
ntpd daemon fails to start because it is not able to resolve the FQDN name of the NTP server.
This attempt to resolve the server's FQDN is done only once.