Need beds but there are enough?

[Bluedu]

My drakes need a place to sleep. I'm new in winter, so I've built a heater next to the beds but still they won't sleep in most of them? why?

[VooDooU]

mine wont sleep in any of them, find anything?

[Bluedu]

I had to build new ones, because of the winter. I dont know why this happened.