Does Qur'an give the grandchildren the right to receive the inheritance from their grandfather for their dead mother? The grandfather died after his daughter. When they asked their right in their mother's heritage part in her father, they told them you have no right in it? I hope I expressed well the question. What should they do to get their right? They live in Palestine.

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
According to the Islamic Shariah grandchildren do not inherit from their maternal grandfather but they may receive through the will left by the dead person provided the will does not exceed one third of the whole inheritance.
Furthermore, your mother also does not inherit from her father since she died before him. The basic condition for getting inheritance is being alive at the time of a person's death. If your mother died before her father, i.e. your maternal grandfather then she does not have any right in the inheritance of her father.
Despite this rule, it is likeable for the other inheritors to grant you (grandchildren) something to reconcile your hearts.
Allah knows best.