I configured the IP address on my new device, saved the changes, and am now unable to access the device, what happened?

This is normal operation. When setting up a unit for the first time, you are on the default IP address of 192.168.123.123.  When you change this IP, the 192.168.123.123 address is no longer valid and the device and the computer connected to it are no longer on the same network. 

To communicate with the unit, you will need to reconfigure the computer to be on the same IP subnet as the device or connect it to the network and access it from a network connected computer.