وَكُلُّ دَعْوَى النُّبُوَّةِ بَعْدَهُ فَغَيٌّ وَهَوًى
Every claim to prophethood after him is error and desire.
A claim to prophethood is a person asserting a prophetic office for himself. Since the prophetic succession ended with Muhammad ﷺ, later claims of that kind are invalid.
They contradict the doctrine of the Seal of the Prophets.