How do I coach a rep who won't change or can't close?

You have grown into coaching, and that is a real shift from selling yourself. What frustrates you now is the reps who will not change or cannot close, and that frustration makes sense, because you can see exactly what they should do and they are not doing it. But their progress is not fully in your hands, and that is the hard lesson of coaching. There is a difference between the rep who cannot and the rep who will not, and they need opposite things. The one who cannot close needs a specific skill broken down and drilled. The one who will not change needs a reason that matters to them, or an honest conversation about whether this is the right seat. Treating both the same is why you stay stuck. With your most frustrating rep, get clear on which one they are. If it is skill, pick the single thing costing them deals and work only on that. If it is will, have the direct conversation you have been avoiding. You cannot want it more than they do. Your job is to give them a real path and then let them choose to walk it.