I bought a clove coral (clavularia) from one LFS few weeks back. I shared this coral with a friend. The coral did'nt make it in both our tanks, although it was in the pink of health at the LFS. Both of us did what many people would do, take the coral out of the bag and put it in the tank.
Few days ago, I went back to the same shop and bought another clavularia. This time I dripped acclimatized it for about 4-5 hours. Next day, it was opening already.
For those who cannot figure out why you can't keep certain corals, try drip acclimatizing them. It does help.