A few seconds before…
Max had just helped Sera recover from the panic attack she was having with his charm's hypnotic effect.
Then, thinking he could continue without worry, he had just started worshiping her lips again when he felt her recover her senses, rendering his charm useless.
Although he wasn't consciously using it, his charm was still very potent especially after he became a Four Star Mage, and unlocked the first shackle on his bloodline.
He could confidently say his charm was now potent enough to even affect some weaker Five Star Mages, and very few, if any, Four Star Mages could hope to resist his charm and it should be only possible if they managed to detect the anomaly caused by his charm in themselves.
If they fell prey to it, like Sera had, there was no chance they could regain their senses unless someone helped them or Max, himself, retracted his charm.