One hen won't roost on perch

Hi all, I've been a chicken keeper (3 hens and 1 rooster) for 6 months now, when we first got them we converted an old shed we had in the garden into their coop and closed off the area of fencing around d as a run, however after autumn was over and winter started the rats flocked in and every week we were finding new holes in the shed that we had to cover, after we started seeing the rats during the day we decided it was time for a more secure coop (we live next to a river and a field so rat extermination isn't really a viable option, we decided to make a new coop as rat proof as possible) anyway, we bought a coop ready made and built a run that we fully covered and put hardware cloth all along the bottom so the rats cannot get in. Anyway, 4 nights in and one of my hens just will not roost on the perch, she always used to, and there is plenty of perch space but it seems if I go out an put her on the perch 10 minutes later she will either be in the nest box or on the floor under the other chickens, obviously both are not exactly what we want.. does anybody have any advice on what I can do to get her up with the other chickens? It is a house shaped coop with a pointed roof in the middle, 2 roosts parallel to each other but I don't know if there is room for another perch in there.

Hi and welcome

Three possible reasons for this behaviour that I can think of off the top of my head....

1. Not enough room on the roosts and she is being bullied into sleeping on the floor or nest box. Is she perhaps bottom of the pecking order?

2. She is ill and doesn't feel strong enough to roost.

3. She is going broody.

Do any of those sound like they may be applicable?

Broody that's what was thinking to..

Not sure about broody, she has been laying for about 2 months but she comes out of the coop into the run during the day. Is it possible to be broody just at night? Unless because she is young she is a bi confused?
Health check regularly and can't see any signs of ill health or pecking.
In my flock strangely the rooster is on the bottom, he isn't the most clever of the flock and I think the girls realise that.
I will have to keep an eye out for any bullying that's going on.

Welcome to BYC! I'm glad you joined us!

Hi and welcome to BYC. I'd suggest that its not broodiness if she is not sitting during the day - usually nighttime nest sitting is a sign of going towards "total broodiness". I'd follow other suggestions made by Rebrascora and see what you come up with.

All the best
CT

Maybe in the previous coop, rats were after them on the roost. That's a hard scene to blot out. Could you rent a couple Jack Russell terriers for a couple of days?