If you're struggling with one of you characters, try writing a letter as your current character to their older or younger self. Think of what they might want to tell their past or future self, this might help you pinpoint what's important to your character.
Write a pivotal scene in your novel from a different character's POV. For instance: at a funeral, you may have written the grieving widow's thoughts and feelings. Write about that funeral from the deceased husband's POV, the eldest son's, or the step-sister's.