I just confirmed that live-reload works fine with the plugin you linked me.
The issue is vagrant. Vagrant mounts stuff in a terrible way and breaks inotify/kqueue file change notification. This leaves you stuck with all file watching broken from what I can see.
I recommend you avoid vagrant and just do a local Discourse install.
For my test,
- I checked out your plugin
- Ran
bin/puma - Edited header.scss and added `body { background-color: red !important; }
- The background turned red, no need to reload the page or anything.