The commentators ask: Isn’t it true that there is nothing that stands in the way of repentance?
It is brought in the sefer Zichron Eliezer from Rabbi Shlomo from Sassav as follows: The heavenly voice that calls out has the capabilities to inspire all who hear it towards repentance except for Acheir. He can hear the voice, but he will not become motivated because of it. If he would have decided to repent by himself, it would have been accepted.
A parable is given: A son was constantly rebelling against his father and the father’s rebuke was not resulting in any positive change at all. It came to a point, where the father simply gave up and informed his son, “From now on, I will not be reprimanding you anymore – you are on your own.” If the son would reflect upon the words of his father in a serious manner, he would become brokenhearted that his father has become so disgusted with him that he will not even be admonishing him; this will propel him to regret his past actions and beg his father for forgiveness, which he knows will be accepted.
The Shalah explains in a very similar manner: The Gemora Pesachim (86b) states: One should listen to everything that the host tells him except to leave. Even if the Holy One, Blessed is He notifies a person that he will not be assisting him any longer and it is as if he is being chased out of this world, it is incumbent upon that person to gird himself and harness all of his strength to repent and ask forgiveness; if he accomplishes this, there is no doubt that his repentance will be accepted.