Lap is particulary hard to eat IME. I have had new endli, Buetti, Delh, Koliba and they all eat right away. But my lap took about 1 month to start showing interest in food and finally after 6 weeks, he started to eat krill. Still refuse shrimp and silverside, but it's just a matter of time before he decided to eat.
They won't starve to death, just keep throwing food once a week until he decide to take it. If he doesn't take it, remove the food, wait another week and try again.
Bichirs are natural hunters, they won't starve themselves to death