Why doesn't the controller accept an object back from the View?

Question

Java

Why doesn't the controller accept an object back from the View? There is such a situation that the absentDAO object should come to the controller with the address "/teacher/createLesson/confirm", but it comes empty.

Controller text. The first sends data to the form, the second is responsible for receiving it.

@PostMapping("/teacher/createLesson")
    public String postCreateLessonChoose(Model model, Principal principal, @RequestParam(name = "goodGroup") String goodGroup, @RequestParam(name = "goodSubject") String goodSubject){


        //Select info from database
        APP_User user = userRepository.findByUsername(principal.getName()).get();
        Group group = groupRepository.findByName(goodGroup).get();
        Subject subject = subjectRepository.findByName(goodSubject).get();
        List<APP_User> students = userRepository.findByGroup(group);

        //Create list with absent
        List<Absent> absents = new ArrayList<>();
        absents.add(absentRepository.findByName("Присутствует").get());     // be careful!
        absents.add(absentRepository.findByShortname("НБ").get());

        //Take current date
        DateTimeFormatter d = DateTimeFormatter.ofPattern("dd.MM.yyyy");
        String date = LocalDate.now().format(d);

        //DAO for form in frontend
        createAbsentDAO absentDAO = new createAbsentDAO();
        for (int i = 0; i < students.size(); i++) {
            APP_User student = students.get(i);
            absentDAO.addObjectToList(new AbsentWithStudent(student.getId(), student.getFirstname(), student.getLastname(), absents, date));
        }

        //Sent DAO to frontend
        model.addAttribute("absentDAO", absentDAO);
//        model.addAttribute("absentList", absents);


        return "/teacher/createLesson";
    }

    @PostMapping("/teacher/createLesson/confirm")
    public String confirmCreateLesson(Model model, @ModelAttribute createAbsentDAO absentDAO){

        System.out.println("DAO count: " + absentDAO.getList().size());


        return "/teacher/main";
    }

Code from the form:

<div class="row justify-content-center">



    <div class="col-6 mt-4 shadow p-3 mb-5 ml-3 mr-3 bg-white rounded">

        <p class="mt-1 mb-1 font-weight-light text-primary h2 mx-auto bg-white rounded">Выбор предмета и группы</p>

        <form action="#" th:action="@{/teacher/createLesson/confirm}" method="post" th:object="${absentDAO}">
            <table class="table table-bordered">
                <thead>
                <tr>
                    <th>Студент</th>
                    <th>Data</th>
                </tr>
                </thead>
                <tbody>



                <tr th:each="dao,itemStat : ${absentDAO.list}"  th:field="${absentDAO}">
                <td th:text="${dao.lastname}" th:value="${dao.lastname}"></td>


                <td>
                    <select>
                        <option th:each="absentList2 : ${dao.absentList}" th:value="${absentList2.shortname}" th:text="${absentList2.shortname}"></option>
                    </select>
                </td>

<!--                                             HIDDEN!!!!!-->
<!--                <input type="hidden" name="group" th:field="*{group}">-->
                </tr>
                </tbody>
            </table>

            <button type="submit" class="btn btn-primary mx-auto">Создать</button>
        </form>
    </div>


</div>

The object that is returned to the second controller: