Egg spawns are a little weird. Ppl have to be around, and theres a timer that applies to all your (female)tames. When timer is up there is a percent(unknown to me) chance an egg will be laid. Having mate boost and oviraptor increases this percent. But only so many eggs can spawn with a certain area so this leads to dinos "laying" eggs but no actual egg spawning.(ever notice poop floating under a dino)