Don't be sad as my Percula and Anemone don't co-exist together either
Here's an analogy based on what I have noticed so far
-If your water quality is bad
-If your lighting is not sufficient
-Setup (liverock/livesand organization) not good
-And number of other reason
Anemone usually moves around to find a good place. So, clown notices that and stays away from the anemone.
But when you meet all the above requirement, anemone sticks to one spot and clown realizes that to be a steady home
Although I'm not successful yet, I notice my Percula at least checking out my Long Tentacle Anemone. Two times he almost landed, but decided to wait longer.
I heard (exp folks, please correct me) Maroon Clowns are most likely to choose a host over other clowns.
While it is not advisable to mix species, if I don't see my percula choosing the anemone, I am going for a maroon one (later might trade the existing one. Seeing clown in an anemone is one of the significant reasons why I am in this hobby!