What should a husband do if his wife is sexually averse to him, rejects his intimate advances, and does not respond to him in a way that achieves marital happiness, despite his attempts to reach an understanding with her, all within their first year of marriage?

The wife is suffering from a psychological problem, which might be shyness or a crisis related to the relationship, and requires the help of a psychotherapist. If she refuses, remind her of the obligation to obey you in bed, as it is fundamentally and detailedly obligatory unless it involves disobedience or is abhorrent, according to the saying of the Prophet, peace and blessings be upon him: "If a man calls his wife to his bed and she refuses, and he spends the night angry with her, the angels curse her until morning." You can seek assistance from people close to her or from her family to persuade her to accept specialized treatment, as it is the only way to deal with these crises.