部署到Vercel后，无法在以下函数中设置Cookie：

const logIn = (req, res) => {
  const { email, password, cookieAge } = req.body;
  const throwError = (res) => res.status(500).send({ message: "The credentials are incorrect. Please try again." });
  let userFound;
  User
    .findOne({ email: email })
    .then(user => {
      userFound = user;
      return bcrypt.compare(password, user.password);
    })
    .then(passwordValidation => {
      if (passwordValidation) {
        const token = jwt.sign({ userId: userFound.id }, process.env.JWT_SECRET);
        // console.log("token:", token);
        res.cookie("access-token", token, { maxAge: cookieAge, domain: ".vercel.app" });
        res.json(true);
      } else {
        throwError(res);
      }
    })
    .catch(() => throwError(res));
};

以下是响应头：

那么问题出在哪里呢？