The following message is shown for valid FQDN entries (one or more):
"IP <ntp_fqdn> is invalid"
The validation logic incorrectly assumes only IP addresses can be provided as NTP servers. As a result when an FQDN is provided it reports back that it is unable to accept such a value.
Currently there is no resolution. This will be fixed in the future release.
To workaround the issue, use the IP address of the provided FQDN of the NTP Server.