First and foremost, grandparent’s rights/visitation is rare and very difficult to obtain. A grandparent has rights to visitation in only a very limited set of facts. In essence, your child, the parent of your grandchildren, must either be deceased or their rights terminated AND the other parent is refusing to allow you to have contact with your grandchildren. See NRS 125C.050.
The constitutional rights of a parent to choose how to raise their children is extremely strong in the law and if your child is alive and well and caring for their own children (your grandchildren), them not allowing you to see your grandchildren is NOT a basis to petition the court for visitation.