Thanks for the feedback! I wonder, were you holding down right click? The way to do it is to hold it and approach a snake segment. When close enough, it will get highlighted white and the time slows down. Then you can let go and the snake bites down.
Another reason could be you were too small. It is not in the tutorial unfortunately, but three body segments act as your core. You cannot eat them or lose them, when hit you lose health. Any extra segments on top of that you can eat and will get destroyed instead of health when you are hit.
Thanks a lot for giving it a go anyway!