Read the ending after لَنْ.
● لَنْ يَخْلُقُوا ذُبَابًا — They will never create even a fly. The original plural ending would contain an inflectional nūn; here it is removed. (Al-Hajj 22:73)
● لَنْ يَدْخُلَ الْجَنَّةَ — He will never enter Paradise. The first-group final dammah has become fatḥah. (Al-Baqarah 2:111)
● لَنْ تَنْفَعَكُمْ أَرْحَامُكُمْ وَلَا أَوْلَادُكُمْ — Your relatives and children will never benefit you. The verb is first group, so it ends in fatḥah. (Al-Mumtahanah 60:3)