FWIW,
I had a couple of zoa frags that were doing fine then quit opening up. I was advised to do another Revive dip followed by a pH and temp adjusted dip in FW, all the while "blowing" them with a turkey baster.
A LOT of tiny (and some not so tiny) amphipods came off the frags. They were irritating the zoas.
Since then, they have been just fine. Ever since, I call this procedure giving them an "attitude adjustment"...
If you can't take them out of the tank, try gently "blowing" them in between the polyps with a turkey baster and see what comes out, if anything. There can also be detritus buildup in there as well (been there done that).
HTH