The Juicebox plugin for Lightroom requires Lightroom 4, 5, 6, Classic CC 7 or higher.
This is noted on the plugin's own support page here.
(The plugin will not work with Lightroom CC.)

In late 2017, Adobe split what was then known simply as Lightroom CC into two separate products. Lightroom CC became Lightroom Classic CC (currently on version 8.2.1) and Adobe released a new version of Lightroom under the name Lightroom CC (currently on version 2.2.1).
Unfortunately, the new Lightroom CC does not accept third-party plugins or web engines so it is not possible to use the Juicebox plugin with this version.

There are other ways to create Juicebox galleries, though (you do not need to use Lightroom).
You can use JuiceboxBuilder (the standalone desktop program to create and edit galleries) or the Juicebox Photoshop Template (if you have Photoshop) or you can create a Juicebox gallery manually using the sample 'web' gallery as a template following the Manually Creating a Gallery instructions.

I hope this helps to clarify things.