I have a pair that have been my DT for over a year and a half and won't go near anything. They are hosting a top corner of my back wall. I even have another clown that is hosting in the same tank and if a nem walks up the wall to them they stay clear of it.
There’s a list on here somewhere of what species of clownfish naturally host which species of anemone. Short version is they aren’t always compatible. There is also some speculation that captive bred fish may be less disposed to host.