My chickens have decided to stop using the coop

[Katie_cluckins]

I have 2 older girls and 4 young chick's and they all cooped together without problem but I extended the coop and since doing that NONE of them will go inside at night, I've seen them pop in and out of it and hang out there but come nighttime they won't go in. Any idea why?
I also adopted a baby duck and they are separated at the moment coz duck is too small when is the right time to get them together I don't want duck lonely

Do I need to change the design?

 

[STACEYH]

In the evening place your chickens on the roost. This may take a bit for them to understand that is where they belong.

 

[CapricornFarm]

Maybe they saw a rat or snake in there?

 

[Crazy Maizie]

Is your coop safe from predators? Where do your chickens go when they don't roost?

Your duckling should have a duck friend. It could get picked on by the chickens even once it is older. It's almost always better to have 2 of the same species especially when you integrate.

 

[rosemarythyme]

You extended the coop or built a new one? How much roost length is there right now vs before?