Some chickens will be floor layers no matter what you do. One of mine was a floor layer,tried everything to no avail. She was the first to start laying. Others all used the nests. But after 7 months for her own reasons she did start to lay in the nests and left the floor. If you research poultry studies or read texts on nest vs floor layers some just do it and others don't and no one has an explanation. And most of early floor layers will eventually move to the nests.
Just make sure nests are easily accessible and chicken friendly.