4 happy conure & 1 not so happy

[Wolf]

Some times we may not be listening to the bird as well as we should and either miss what the bird is trying to tell us or we misunderstand what they are trying to tell us.
If the other birds are doing fine and want to interact with you, perhaps the best approach would be to work and play with them and let this birds own natural inclination towards being a part of the flock as well as it own curiosity come into play and let him come to you first. This should not be about changing the bird to suit our concept of how they should be, rather it should be about the relationship that you develop with the bird, and truthfully, I don't see much of a relationship until the bird is ready and willing to approach you of its own desire.
I have very often used my other animals and our relationship to reach through with another one when I could not do it myself. They do observe, talk and learn from each other much more readily than they do from us.