Which app are you using? For most of them I needed to get a few feet away, as mentioned in the article. For some it seemed I needed to be more exactly facing it, not angled. I got all of them to scan pretty easily.
I'm using the default camera on my phone. It's called "Camera". The phone is a Samsung Galaxy. I've tried it close, far, angled, straight, big, small. I haven't gotten any of them to work a single time.
Works mostly fine for me from Firefox on Android. All scans fine except one.