Snakes use their sense of smell to determine pray items, not just heat signatures. When you get mistaken for food it's because you smell like rats/mice. Also after being shipped his is striking at you as part of his defense not out of hunger.
Most people recommend waiting a week before offering food. I feed my snakes on a schedule and offer new additions food when my QT room is being feed. If they don't take it, I don't push it. They get offered, if they refuse then they get to wait until the next feeding. So in short, you could try tonight or tomorrow but if he doesn't take it leave him alone for a week and then try again.