Custom notification plugin gem I created not working

Hello, I found a gist somewhere instructing how to create a Jekyll plugin that shows Jekyll build notifications using macOS notifications. I dumped that code into a .rb file in the _plugins directory and somehow managed to make it work fine.

I decided I wanted to put it into a gem and load it onto to share with others. I build and deployed the gem successfully.

However, even after including the gem in my Gemfile and running bundle install, the notifications do not fire. I ensure that safe: false and disabled the Github Pages gem. I did confirm that the gem is installed on my system.

Here is a link to the gem that I built:

Is there a way I can verify that this plugin is loaded as a gem?
Is it possible that the code in this gem just wouldn’t work bundled as a gem?