All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If you had continued reading the words of Ibn Al-Qayyim which seem awkward to you, you would have found the answer to your question.
After quoting Ibn Taymiyyah as transmitting the two views regarding whether or not the receiver of the act enters Paradise, he said:
“The fact of the matter is, it is to be said that if one afflicted with such an affliction repented and returned to Allaah, and was blessed with sincere repentance and righteous deeds, and he was better in his old age than his youth, and he replaced his bad deeds with good deeds, and he washed the shame of that sin from him with a variety of good deeds and acts of worship, and he lowered his gaze and protected his private parts from what is forbidden, and was sincere with Allaah in his interactions, then such a person would be forgiven and he would be among the people of Paradise, as Allaah forgives all kinds of sins. Since repentance does away with all kinds of sins, even idolatry, killing Allaah's Prophets and allies, magic, disbelief and so on, then Allaah's forgiveness will not fall short of forgiving for such a sin …. On the other hand, if the receiver of the act was more evil in his old age than in his youth, and he was not blessed with sincere repentance, or righteous work, or he did not rectify what he had done, or replace his evil deeds with good deeds, then such a person will most likely not be blessed with an ending just before death by which he will be allowed to enter Paradise, as a punishment for his deed, because Allaah punishes for a sin with another sin, and the punishment for sins gets doubled in the same manner that Allaah rewards for a good deed with another good deed. If you look at the case of many dying people, you will find that they are prevented from a good ending to their life as a punishment for them for their evil deeds.” [End of quote]
This statement from Ibn Al-Qayyim shows that he favors the view that the receiver of the act will enter Paradise and his affairs will be set right if he is blessed with repentance. But if he does not repent, then such a person will not be allowed a good ending at the time of death by which he enters Paradise.
Also, these words of Ibn Al-Qayyim do not suggest that one who does not repent from this sin will never enter Paradise, even after being punished if he was a Muslim; rather, such a person is under the Will of Allaah, as Ahl As- Sunnah agree upon. For more benefit, please refer to Fataawa 5087 and 88067.
Allaah Knows best.