Would try getting some crickets or live food and throwing one at time. In between throw in some tilapia or broken up pellets. Throw in a powerhead.
This will work well with soaked carnisticks that are halved.
May need to starve a few days and try and retry. Don't starve for weeks at a time. These fish are strictly live food in the wild and in the lfs (likely).
If all else fails then try feeder guppies that are qt'd and pretreated with meds. Healthier and available feeder.
I've feed him livery foods for a while , I want to wean him only like foods, he is 4 inches long. He is very shy, if I add feeders in he will not eat them for a few hours.