Do you have all hatchery chickens ? they are bred to not go broody ...
Rarely they still do ..
You could try giving them feed with soy..that might influence them to go broody ..
As it is hormonal .....they go broody when they get the hormones ..Soy Mimics hormones in a body .
or Get some chickens ..from a breeder
or Sumatras , Silkies or ?
I have all breeder and backyard birds, no hatchery birds. I have a young Ameraucana who puffs up and yells at me when she's on the nest. She will sit for several hours, but always leaves. I have put eggs in with her and she tucks them right under her.