Every manager meets this rep sooner or later.
Short answers in the debrief. A field day that keeps moving. "Everything is fine, no need."
The easy reaction is to push harder. More field days, more follow-up, a firmer tone. In my experience, that turns resistance into silence.
Resistance is information. It usually means the rep is protecting something.
What I have found works:
Ask, plainly. "How are our field days working for you?" Then listen properly.
Listen for the reason. Very often it is fear of being judged, not dislike of learning. Some reps have had managers who used double visits to build a case against them. They remember.
Say what coaching is for. "This is about your development. It is not a report on you." And then make sure it is true.
Let the rep choose. The skill, and the doctors for the next field day. Ownership lowers the guard.
Keep the first visit light. One skill. Start the debrief with what went well.
Keep your word. Follow up on the one skill, and no surprises at review time.
Many reps who get called "uncoachable" are simply waiting to see if they can trust the process.
“A rep who resists coaching is usually protecting something. Find out what.”
Lesson 9 of 23 in Step 4: Coaching, with the full guide and a checklist for this week.