Orange Cup Coral won't open

[Geofrog]

Just recently added an orange cup coral and have been trying to get it to open up to feed. I have tried isolating it in the tank and in a separate container while feeding it mysis. Last night it started to puff up and I could make out a few tentacles emerging, but this morning it was all retracted again. I know that once the tentacles are extended, feeding it will be easy. So I'm looking for ideas as to how to get it to extend the tentacles.