What are your water parameters? Do you add iodine, strontium, and molybdenum?
I just bought my Xenias two weeks ago. I have a 55G 4ft tank with (a) Bubble Coral, (b) Green Star Polyp (the waving kind), (c) shrooms, (d) finger leather frag, and (e) Kenya tree. I have a CUSA Orbit 4x65W Actinic/Daylight PC fixture. I have two HOB powerfilters and a Prizm skimmer.
The xenia came from a metal halide display tank at an LFS. I drip acclimated it. Then I placed it low in the tank while it was on actinics. It was retracted at first. But now, man, that thing is rockin'. It's the thin-tentacled kind. not the thick-ultra pulsating diamond looking tentacles. And the thin tentacled ones don't pulsate as much. But boy, that thing was pulsating after a few days. Normally at night.
Give it a day or two more to see whether it will acclimate with your light. Make sure that water current is present for it.
Try to feed the tank with phytoplankton. See if it would start pulsating to feed.
However, before you start adding stuff, test your parameters and make sure you have a good one first. I am pretty sure you do if you have kept your other specimen for a while now.
Good luck.