Acknowledge his disinterest in coaching. Be curious and ask him to share reasons for his disinterest. Stay curious and be genuinely interested in his position. Do not try to offer any counter-arguments at this stage of the conversation. As Dr Covey says: "Seek first to understand".

Start by going over the goals for coaching and how the process is going to go. Sometimes disinterest can come from lack of understanding or unclear goals. But as others have written, you can't force it. Acknowledge the detachment and talk honestly about if coaching is the best choice at the moment.

It may be there are underlying vulnerabilities the client does not feel ‘safe’ to disclose. ? We don’t know the circumstances here - e.g did the person ask for coaching or were they assigned by a line manager? Commitment requires engagement and developing trust. It’s not a transactional process.