A few things to try:
- Raise the temperature of the water. Sometimes the higher temps will trigger feeding.
- Make sure he has a suitable cave/hideout that he feels comfortable in
- Cant tell from the pics if he's in the tank by himself. If he is, try adding other fish. If he sees them eating, this may trigger competitive feeding or train him to take the food.
- Dim the lights. Mine hated bright lights and was most active when the lights were subdued, especially at dusk and dawn
- Dont give up. Mine took about a month before eating anything. Once he started, he was a voracious eater and grew very quickly. Primarily live redworms/red wigglers and fish fillets.