In order for DirectAdmin to be able to run on your system, 3 things must be true:
1) The licensed IP must exists on the box. Type /sbin/ifconfig, and you must see the licensed IP in the output.
2) The licensed IP must function and be able to be bound to, eg:
wget --bind-address=1.2.3.4 http://www.directadmin.com/index.html
3) the IP that connects to our server must be the licensed IP.
If you only have a LAN with 192.168.x.x IPs on it, they would not satisfy rule number 1 and 2.