I used to keep many apple snails, if that's what you have.
The eggs can't hatch underwater (it would drown the embryo's) so the snails lay them above water, however sometimes there isn't enough humidity in the air and the eggs closer to the surface will dry out (usually I'd still get a few babies to hatch/ ones on the inside of the clump of eggs). Another reason you may not be getting baby snails could be that you have only females (apple snails are one of the species of snails that have 2 sexes, so they need male and female to produce babies) however females still lay eggs even without males present. Also like mollies the females store sperm, so you could be getting some eggs fertilized (why you had a few babies before), but all the ones being laid now are not.