my chickens refuse to sleep in coop.

[stretchy4u2]

I have 17 chickens and they sleep in my tree outside my window at night. Is there anything wrong with that.

 

[Percheron chick]

Sleeping in the tree makes them easy targets to be picked off by owls.
Post pictures of the coop. There might be something obvious that makes them stay out.

 

[rebrascora]

Depending upon your location and possible predators in your area and the climate then yes there may be a problem. Do you have a secure coop? If so, you need to work out why they are not using it. Did you home them to it when you first got them? Do you leave a light on in your room which may be attracting them to roost in the tree near it rather than go into a dark coop.

 

[wamtazlady]

Whenever I have had chickens that insisted on sleeping in the trees, those chickens had short lives. The birds would often perch too high for me to catch them and put them in. The owls had no problem catching them.