Aloha Oldsoldier,
Two things with cotton balls...
1. Make sure it is cotton and not nylon or some other material. Yours might not have been cotton if a lighter wouldn't light it.
2. Fluff if up first. The more light and airy you can make it, the easier it will take a spark.
I hope that helps. If you want to "cheat" to help your cotton ball take a spark (although, if you fluff it, you really shouldn't have to), you could cut a short length of jute cord, unravel it all up to its tiniest fibers, and kinda put it on and around your cotton ball. If that doesn't take a spark, I would be extremely surprised.
I did the fluffed up cotton ball with the jute cord for my wife's first attempt with a Magfire a year or two ago, and she was able to get it started right up. I wanted to make sure it would start so she wouldn't get discouraged. In fact, she started to get hooked on the preparedness and outdoor survival stuff at that point. Well, hooked may be a little of a strong word, but she will carry a PSK when she is out now. And her reaction to the fire starting was, "COOL!" And she will periodically ask to start the fire.