Because version 2.3 is a legacy release, it is no longer the primary download on the official Ubiquiti site . You can find current versions and their modern replacements through the following channels:
Required to run the .jar file.
Helps find devices that are unreachable via the controller due to configuration errors. ubnt discovery 2.3 download software
If you are working with extremely old "legacy" hardware and must run the version 2.3 .jar file, you will need to: Because version 2