Best way to get them to sprout is to wrap them up in moist paper towels and put that into a plastic bag and put it in a warm spot for a few days or so....
Where did you get the bulbs?
I've gotten about 5 packs of these so far, I've also found your fish can affect the growth too.
In a tank with 2 plecos and a betta they took off and are overtaking the whole tank. But in a tank with tetras and guppies they died because the sprouts were eaten as soon as they came out.