What is the ruling on a marriage contract without reciting the marriage formula, and what should be done after approximately four years have passed since this marriage?

If the woman's guardian says to the husband, "I marry my daughter to you," or "I give you my sister in marriage," and the husband says, "I accept her marriage," and this occurs in the presence of two just witnesses, then the marriage contract is concluded. As for the Khutbat al-Hajah (Sermon of Need), it is sunnah (recommended) to deliver it, and omitting it does not invalidate the contract. If what is meant by "formula" is the offer and acceptance, then the contract is not valid without them, and it must be renewed.