Things to try if your character refuses to work with you.
I have here three different methods of how to fix such a problem.
Write the scene from a different point of view.
Write in a different tense.
Write in opposite of first or third person.
For my examples I will use the following scenario:
In a dungeon, your Hero has just released the Love Interest out of the cell when the Villain casually walks in and interrupts them.
But now your Hero freezes up and refuses to say his lines.
1) Write from a different POV.
How does the scene look from the Love Interest's eyes? Does your Hero's voice shake when he addresses the Villain? Does he back up? Does he put a protective hand on you, his girl?
2) Write in a different tense.
Instead of (past tense):
The Hero lifted the sword and held it toward the villain.
Try (present tense):
The Hero lifts the sword and holds it out towards the villain.
Or vice versa.
3) Write in opposite of first or third person.
Meaning, if your scene is written in first person, trying writing in third person to get a new perspective.
Instead of (first person):
I eyed Villain as he circled around and shut the cell door, making it slam. I wince at the sound, remembering how many times a door had been shut in my face. Love Interest wrapped her arms around me, and I could tell by her silence that she was holding her breath.
Try (third person):
Hero eyed Villain as he circled around and shut the cell door, making it slam. Hero winced at the familiar sound from his childhood. Love Interest wrapped her arms around Hero and held her breath.
Or vice versa.
Hopefully trying one of these three methods will help bring a new angle to your scene, and help you get your Hero back into his role.