The magnesium is intented to be a "first tinder", rather than a complete tinder. It burns hot and FAST. You need to have a something more substantial in the way of tinder-like material, but unlike true tinder, tinder-like can be less than perfectly dry. Not wet, just less than perfect.

As for how you were scraping, let me guess- stainless steel blade, using the edge? Carbon steel works better, and if the spine of your blade is square with a decent corner, it will work much, much better. Or the back of a hacksaw blade.

If you use it right and take your time, mag blocks work much, much better.