PiHole and DNS setup

I have my router set to use PiHole (HornPiDNS) as the DNS server. When I do nslookup on the other nodes I am able to find the IP address for the other nodes I have setup up. When I lookup my PiHole host HornPiDNS, I get:
** server can’t find hornpidns: NXDOMAIN

If someone could point me to some documentation that shows how to setup HornPIDNS I would appreciate the assistance.

In /etc/dnsmasq.d/02-mydns.conf file I have:
addn-hosts=/etc/hosts.mydomain

In /etc/hosts.mydomain I have:
192.168.254.1 HornPi HornPi
192.168.254.2 HornPiDNS HornPiDNS
192.168.254.6 HornDesktop HornDesktop
192.168.254.254 Router Router

That means when you do a

nslookup HornPiDNS

it always returns NXDOMAIN regardless if you do it on the Raspberry Pi itself or on any other device?

And similarly the other entries all work regardless on which device you use nslookup?

Just by chance: Did you restarted dnsmasq after modifying the files?

I have restarted multiple times. Part of the issue is when trying to get to the pihole web page (http://hornpidns.home/admin) doesn’t work but http://192.168.254.2/admin works.