Lucifer loses his mojo due to profound self-loathing and a crisis of identity, specifically after killing his brother, Uriel, to protect Chloe Decker. He regains this ability in
Frantic to find Chloe after she is kidnapped by Michael, Lucifer’s mojo spontaneously returns. During this same episode, he also discovers he has regained his invulnerability near Chloe, no longer bleeding when he is shot in her presence. Why Did He Lose It? what episode does lucifer get his mojo back
So, if you want the moment he becomes a powerful angel again, it is . Lucifer loses his mojo due to profound self-loathing
Dr. Linda Martin suggests that being intimate means sharing power. When Lucifer felt insecure about his place in Chloe's life or feared being unworthy, his powers went "on the fritz". specifically after killing his brother