Should be pretty. Flat side goes down,

just in case. And it must be on the sand bed. Let it rest a day or so, then get some storebought shrimp (people food) and slice one. Hold it above the plate with the pump off and squeeze the juice out of the shrimp until you're sure some got to the plate. Withdraw shrimp. Turn pump on. If tentacles turn up, try shrimp chopped, and put it on the center of the plate, protecting it from fish. Leave it about 5 minutes, then turn on the pump and let the shrimp float. Eventually the plate will respond to this offering and extrude more tiny tentacles.
Mine, an orange, has great color and extension day and night, and eats Formula One Sinking Pellets with Garlic. This is not recommended, but if it can get anything into its tentacles, down the hatch it goes. The only thing I've ever seen get a piece away from it is a mega-bristleworm, and that after a 3 minute tug-of-war.
I somewhat suspect my use of Kent Coral Vite may have helped it a bit. Can't prove it, but certain of my corals have gone very ample since I've been using it. The plate is particularly so, also the frogspawn. Either that or my water/light is spot-on to their taste.