I have run out of ideas on how to get this to work, now I’m questioning if it is even working…

Yes, things have changed since I wrote this post — the WebAR standard merged with WebVR into a new WebXR standard, and the ecosystem is in progress of adapting to the new standard. A new version of a-frame, 0.9.0, has just been released, and it includes initial support for WebXR. Once things stabilize a bit more, I will update the blog post (and the sample code) to use the up-to-date libraries so the demos work out of the box on modern Chrome browser.