In Chapter 7, two major events have occurred: Gatsby has professed his love for Daisy in front of her and her husband Tom, and while driving they struck and killed Myrtle, a woman with whom Tom has been having an affair. After Nick, the narrator, speaks with Gatsby and gets the story from him, he peeks through a window at Tom and Daisy, to make sure Tom isn't reacting badly:
Daisy and Tom were sitting opposite each other at the kitchen table, with a plate of cold fried chicken between them, and two bottles of ale. He was talking intently across the table at her, and in his earnestness his hand had fallen upon and covered her own. Once in a while she looked up at him and nodded in agreement.
They weren't happy, and neither of them had touched the chicken or the ale -- and yet they weren’t unhappy either.
(Fitzgerald, The Great Gatsby, mrbye.com)
This scene shows Nick that Daisy and Tom are mending their relationship; Gatsby's romantic notion that Daisy will leave Tom for him has been shattered by their sharing of the hit-and-run accident, and she cannot bear to see him. Instead of signaling him to come in, she simply turns off the light, and he goes home miserable and depressed. It is likely that Tom was using the accident as a way to convince Daisy to stay with him, or to claim that associating with Gatsby now would simply lead to her arrest; he also might have been telling her that the past no longer mattered because Myrtle's death freed him from their affair. They have been married for a long time, and their conversation is typical of their past; Tom takes the lead and Daisy, without reason to resist, follows along. Their conversation leads them to leave without contacting Gatsby again, and Gatsby dies hoping that Daisy will remember that she "loved him more" and call.