I've have no experience with sharks, but I do have experience with getting fish to eat.
Fist thing I would do is to isolated into its own tank so that you can control its environment and do controlled experiments, or make sure there aren't other fish in the tank with it.
1. Possible nocturnal feeder.
2. Possibly too nervous to feed in the open, as they need to be defensive once born, otherwise they get eaten themselves.
3. Possibly need to stimulate their attack response. Prey size, movement, etc.
4. Last possibility, and I think this is the likely one, is that its still feeding off it's yolk sac reserve.
The first 3 can be identified easily. Once you have it in a tank, fill half of it with cover and leave the other half open, so it can decide which half he likes better. Next you need to fill with live food, as I think it won't recognize frozen. Try live ghost shrimps and pods you can catch at any of the marine docks along Long Island. Bring a net and just scoop the seaweed mass and catch anything you can. There will be dozens of species of crustacians in there, bring them all back. I would keep the seaweed too as the "cover" mentioned earlier.
Also see if you can get live bait, spearing and worms from any bait and tackle shop. There's a few out here in Queens. Also get live brine shrimp and black worms from Petland.
Next keep the tank exposed to the window so it has a day/night cycle.
Once you're set up, watch and see. I'd use a 5 or 10 gallon QT tank with whatever filter you have. Now the shark will have a variety of live foods to choose from. Don't forget to feed your bait, maybe a few pellets, for the live fish.
Hopefully something will go missing one night. Just keep track of what's in the tank.
Once you've identified what it goes for, you have to start feeding it freshly killed versions of it, then finally frozen.
So if it goes for a ghost shrimp, take out off the shrimps and keep them separate, then take a live shrimp out, spear it on a kabob stick and wave it at the shark. Once it goes for it, you can start using frozen shrimps.
After its trained, it can go back in the main tank.
Personally, I think live food will work, you just have to find the right size. Don't get another shark, they hatch individually and are solo I think. Otherwise shark eggs would be clustered in packs, not scattered around.
In breeding cardinals, the newly hatched fry will ONLY go for moving food that will fit in their mouth. It has to be tricked into thinking the food was alive and I did that by using a pipet and squirting Cyclopeze /live baby brine shrimp mixture into the outflow of the pump.