Joining to a Zentyal Domain controller

[wdar]

Hi,
I am using a Zentyal Domain controller with Active Dir, DNS enabled (Version 6.1 updated) on a laptop.
Win 10 client can join the domain perfectly.
FreeNAS 11.2 installed on a laptop and updated.
All machines are connected to a basic netgear switch and the router is also attached to the same switch, providing DHCP and DNS service as a Gateway.
Network configuration for domain controller is : (IPv4:192.168.137.110/24, Gateway: 192.168.137.1, DNS1:192.168.137.110, DNS2: 192.168.137.1)
// // for Win 10 client : IPv4 : auto from DHCP , DNS1: 192.168.137.110
// // for FreeNAS client: IPv 192.1687.137.121/24, DNS1:192.168.137.110


FreeNAS should join the Domain AD as per the procedure adopted through Installation wizard, but it says "unable to find domain controllers for w.loc"

advise requested pls.