A couple of times. Just let it happen, it may take awhile depending on how developed the embryo is inside. Look through the egg at a light, once the embryo has barely any room fr itself and has consumed the yolk sac it will start tryng to wriggle it's way out.
Best advice for shark eggs I have is consistent good water quality, good flow past them, and hang them if possible so they are not laying on anything and get good flow past all sides.
Also have really fine sand. You could put some kind of tunnel for them to hang out in.and pick up ghost shrimp for them to eat it might take awhile for them to build up an appetite.