zoas never open

happy Friday all. So I have my tank up a couple of years and I have always had problems with Zoas never opening. I read they are an easy coral but for some reason they never open in my tank. I have tried placing in different spots but nothing. I never seem to find a sweet spot for them. my other corals open fine and my water is fine (see below). not sure what the problem is.
I placed on the sand.... middle of rock... rock on sand... low flow... med flow... side of glass on a frag rack. They have been closed for months. any idea what it can be?


dkh 9.2
cal 460
mg 1240
ph 8.2
nitrates 5
nitrites 0