Getting the response of ajax request but the flow doesn't enter in ".then"

request_ajax.js

document.addEventListener('DOMContentLoaded', () => {
            document.getElementById('form-edit input[type=submit]').addEventListener('click', (event) => {
                event.preventDefault();

                let formData = new FormData(event.target.closest('form'));

                const url = '<?php echo BASE_URL ?>home/edit/<?= $_SESSION[md5(BASE_URL) . '_' . 'cLogin'] ?>';
                const params = {
                    method: 'POST',
                    body: formData,
                    dataType: 'application/json'
                };

                fetch(url, params)
                    .then((response) => {
                        response.json()
                    })
                    .then((resJSON) => {
                        if (resJSON.status == true) {
                            alert('Seus dados foram alterados com sucesso!')
                            window.location.href = "<?= BASE_URL ?>home/index";
                        } else {
                            alert('ERRO! Seus dados não foram alterados!')
                            window.location.href = "<?= BASE_URL ?>home/edit/<?= $_SESSION[md5(BASE_URL) . '_' . 'cLogin'] ?>";
                        }
                    });
            })
        })