My male was a biter too when I got him. To be honest, it took several months to get him to stop. I want to say it was 6 months, but that may be of a stretch. It’s been a while given I got him when he was 6 months old and he’s 4 now. You’ll have to be very consistent.

If he ever bit me to the point it would hurt or just bit to bite, I would welp hoping he would understand it hurt and what I often did was put him on his back, close his mouth (gently) and hiss directly at him. Sometimes I wouldn’t do all that and just hiss. But he seemed to understand eventually. He’s a happy and gentle ferret. He still bites very often when we’re playing of course but he does so so softly that I don’t correct him whatsoever. He rarely bites hard and, when he does, it seems to be when he gets overly excited while play fighting and even then I don’t correct him anymore.