Katara,
They usually feed at night after the lights are off, after feeding your fish, turn off your lights and wait around 15-20 minutes then using a flashing light, look and see if he is starting to open. If he is not, hold a piece of shrimp or some type of meating food on the brain and he should start to open. They feed very slow, so you might have to hold the food until he gets a good grip on it. I have trained my brain to feed during the day.
Hope this help,
Ron