“Everything’s all right now, Sheila. (Holds up the ring.) What about this ring?”
Gerald offers Sheila the engagement ring again after it’s revealed that the Inspector's visit was not real, as the family believes the Inspector was a fraud.
Gerald’s decision to return to his engagement with Sheila after the events with the Inspector indicate his desire to return to the status quo and his belief that the crisis has passed. This reflects his inability or unwillingness to learn from the experience, as he goes back to his previous behavior, ignoring the moral lessons that the Inspector tried to impart.