When you set up the LXC container, it doesn't have a fixed UP address. Unfortunately to do that you're going to have to muck around on the command line a little on the Omnia. Specifically you need to edit the configuration file and put the IP address in there, probably the easiest way is for you to log into your router and try
you want to add the following (under network configuration is good, but it really doesn't matter where in the file):
lxc.network.ipv4.ipv4 = <static ip address>
<static ip address> is a fixed address on your network you want to give it.
It would also be good to add the following:
lxc.network.ipv4.gateway = <router address>
<router address> is the address of your default gateway on your network, usually your Omnia's internal network address.
After this you should reboot your container (or the router), and you'll have to go in and reconfigure pihole with
pihole -r and give it the new static IP address.