Invoke not loudly this day! Certainly you shall not be helped by Us.means, no one is going to save you from what has happened to you, whether you scream aloud or remain silent. There is no escape and no way out. It is inevitable:the punishment will surely come to you.Then Allah mentions the greatest of their sins:قَدْ كَانَتْ ايَاتِي تُتْلَى عَلَيْكُمْ فَكُنتُمْ عَلَى أَعْقَابِكُمْ تَنكِصُونَ