SPA 3012 needs to connect to a router

I purchased Flex PBX that uses SPA 3102. I am trying to do build an offline PBX system, but it would not connect once I unplugged it from the internet. What should I do? Does it even work offline?

Voicent software will require an internet connection in order for the software to authenticate your license key. The license key will be checked when you start the Voicent Gateway and before each phone call is placed.

The SPA3102 device does not need to have a valid internet connection as long as it is connected on your local network. This means you will be able to make & receive telephone calls through the device, even though it is not accessible to the public networks.