3ذٰلِكَ بِأَنَّهُم آمَنوا ثُمَّ كَفَروا فَطُبِعَ عَلىٰ قُلوبِهِم فَهُم لا يَفقَهونَAisha BewleyThat is because they have had iman and then returned to kufr. So their hearts have been sealed up and they cannot understand.