Hi Sally,
Let’s try this to troubleshoot:
1. Download the repo – https://github.com/zgordon/gutenberg-course/archive/master.zip
2. Open it in the command line
3. Run npm install
4. Run npm run dev
5. Open a JS file in the /blocks/examples and make a change to it
6. The command line should update
You don’t have to install this as a plugin and test it, just want to see exactly where the problem is happening for you.