It's a bit difficult for us to guess what might have gone wrong without knowing a bit about how you went about the germination process.

I've only sown a cactus mix once, but found it very straight forward. I used the same mix as I used for all my germination. After the seeds were sprinkled on top of the pre-moistened seedling flat, I dusted them with a fine coating of fine sphagnum moss, then misted the flat carefully. I covered all of my flats with a tent of Saran Wrap, and they were all heat via in-soil cables. As I recall, the germination rate was very fast.

I'm sure that others have methods that work for them.