why my 15 month old baby girl always open her mouth ,and she was not smiling at all always very sleepy not at all active

A. Teething could be happening which is why probably your child is trying to show that the child is feeling irritated in the mouth by opening the mouth and maybe the child is not having sufficient amount of food and liquids which is why your child could be done but without a physical assessment since nothing can be confirmed you should definitely check with your doctor