Got the same coop for secondary, our younger birds use it. They used to huddle up and sleep in the nesting boxes, they even tried sleeping in one box all together and some were too big so they had to stand. most of them sleep on the perches now, i used to move them to the perches at night so they couldn't see. By the way, don't ever get that coop. Its a piece of junk. We just got it and and the back door for collecting eggs already broke, the doors don't allow us to latch 1 latch on both the back and the main exit for the run, and the whole structure is a bit flimsy.
I have a problem with one of my roosters and a hen. (who live in the main coop) I try and try and try, but they still don't get it, they can't sleep on the fence or the big perch in the run. They'll go in if i open the side door that i use for collecting eggs and letting them out in the morning, but they won't go in and follow the rest of the chickens through their door and up the ladder to the second floor.