Sometimes they just do that, mine stayed tightly closed up for about 3 weeks, I started to worry a bit, but one night I was feeding and put some cyclopeeze to get all of my other NPS corals to wake up and ready for feeding and my colony poped out and has been out very since. Give it sometime, and keep the food in the water colonm. Make sure it has lots of flow, thay also don't need to be hung up side down, I have mine on the snad bed and horozontail also, both are doing fine.
The key to success is lots of food in the tank, and lots of flow.