One hen will not roost with others

[MontanaLady]

I have a hen that has suddenly become listless and curls herself in a ball on the ground either inside the run or outside but doesn't go in the coop unless I put her there. She won't get on the roost and sleeps on the ground away from other hens. She's the last to come out in the mornings. She doesn't appear sick but I'm a little worried.

I have the same issue. I have 9 hens, 20wks old, & all my other hens roost except one. She sleeps on the floor. There is plenty of roost room & the roost are 2x4s because they prefer to sleep flat footed. She also is the last little lady to come out of the coop in the mornings. She is the most docile hen. I think it is all about the pecking order.