I have mine under a very large figi yellow leather, so it is shaded. But, I will say that when it doesn't open for a time I have to pick it up and dislodge any particles that have landed on it. I do this by shaking off the coral in water that I have siphoned out of the tank during a water change. Soon after doing this it is good to go. I don't really have any place to put it that it is shaded and in a high flow area, so this has helped me. It usually comes out when the halides have gone out, they really don't like bright lighting. They are non photosynthetic, so under a ledge or large coral is the best placement for them.
Dose the tank with filter feeder food when the lights are out, it should perk up quickly.
Make sure everything else in the tank is at optimum levels before dosing of course. Nitrates, nitrites, etc.