Basic checks : You may have already done this.
I think that's your NTP Server IP: 10.1.8.6 ? = It says Reachable, that means controller can talk to it, but it's not syncing. Could you verify once the time skew between controller and NTP server ?
Sometimes, it takes time for NTP to sync. As long as the offset is decreasing = It's a good sign. If it's not or increasing that means something is fishy.
::> date [Ensure the controller's time is within 2 minutes of the time servers' time ?]
::> date -u
::> firewall policy show -policy mgmt [check for ntp entry]
::> network interface show -firewall-policy mgmt
::> network ping -node node-01 -destination 10.1.8.6
::> network ping -lif-owner node1 -lif mgmt1 -destination 10.1.8.6
::> network ping -lif-owner node2 -lif mgmt1 -destination 10.1.8.6
There is plenty of commands to verify, hence please take a look at this KB, it's easy to follow commands.
How to configure and troubleshoot NTP on clustered Data ONTAP 8.2 and later using CLI
https://kb.netapp.com/app/answers/answer_view/a_id/1030530
Thanks!