IPSec VPN Local AD DNS

Good Morning,

First time trying to setup a Fortigate IPSEC VPN for a few remote users. We currently have a in house dns server as well. I can get the tunnel to connect and I can access everything by ip address but not by dns names. I have specified to use the DNS server ip address and I can this it is being issued to the network adapter. But when performing any dns lookup or even a nslookup  I getting the "cant find" message with the ending tag of "Server Failed".

The vpn in using a range of IP addresses in the same subnet and allotment.

Split network is turned off as well. Any ideas what I have missed?