Glad to see you got it working.
However your fix is pulling the cart before the horse. You are the keeper of the keys to your LAN. When you create it, and assign it your LAN address, that's all there is to it. A device need not dictate what it thinks your LAN should be set to. Your Elk device (or any device) allows user input of it's IP configs for this reason.
My advice was spot on, and is the way to manage your LAN. Not it managing you. I suspect your subnet mask was different between your device and LAN. This is all your choice when doing a config. These settings need to be in sync with your LAN across all devices and you have to check carefully that they are indeed input correctly.
#1 rule- There should be only 1 DHCP server on your LAN. Usually your router. Be aware that AP's, many cams, dvr's and other devices all have built in DHCP servers that are usually on by default. They must all be turned OFF. while the devices are all set to DHCP and not static. And devices all on the same subnet mask.
A good router's server will ID your devices based on it's MAC address. It does not care about it's IP address since it will change it to join your LAN. That's how it works. Of course you get to tell your DHCP server WHAT ip you want this device to operate under in the settings.
From this point, troubleshooting, managing or configuring your LAN become a one stop shop inside your router. That is how it is done.