Simple Netlify sample app not working, API_ERROR

I am going through the steps on this page: A Complete CMS with No Server and 18 Lines of Code

It is supposed to create a very small app that can modify a Github repo. It says to create a totally blank repo and then use the two-file app to send some data into the repo. I am not certain how this is supposed to work but when I click on publish it sends an API_ERROR to the screen. This is what appears in the console log of the browser:

react_devtools_backend.js:4026 API_ERROR: Reference does not exist
at new t (
at new i (
at k.handleRequestError (
at k.request (
at async k.patchRef (
at async t.runWithLock (
at async Y.persistEntry (
at async Object.onPersist (

For the script source I have tried both “” and “^2.0.0/dist/netlify-cms.js”. Is there more complete documentation somewhere for this simple application to use Netlify?

Have you checked this: