Why is the form submit button disabled on ios?

Question

JavaScript

Site autoredstar.ru
On the iPhone in browsers safari, chrome and opera (others have not checked), the submit buttons are not active. Everything works on PC and Android. What could be the problem?

the form

<form method="post" action="mail.php">
  <input type="text" name="name" placeholder="Имя*"/>
  <div><span>+7</span><input type="text" name="phone" placeholder="Телефон*"/></div>
  <textarea placeholder="Какой автомобиль вы хотите купить?" name="comment"></textarea>
  <input class="orange-button" type="submit" value="ЗАКАЗАТЬ КОНСУЛЬТАЦИЮ"/>
  <input class="form-title" type="text" name="title" value="Подбор авто: заказ консультации">
</form>

jquery code

$("form").submit(function (e) {
            e.preventDefault();
            var name_input = $(this).find("input[name='name']");
            var email_input = $(this).find("input[name='email']");
            var phone_input = $(this).find("input[name='phone']");
            var fullphone_input = $(this).find("input[name='fullphone']");
            var field_error = false;
            if (name_input.length > 0) {
                if ($.trim(name_input.val()).length == 0) {
                    name_input.addClass('empty_input');
                    setTimeout(function () {
                        name_input.removeClass('empty_input');
                    }, 5000);
                    field_error = true;
                }
            }
            if (email_input.length > 0) {
                if ($.trim(email_input.val()).length == 0) {
                    email_input.addClass('empty_input');
                    setTimeout(function () {
                        email_input.removeClass('empty_input');
                    }, 5000);
                    field_error = true;
                }
            }
            if (phone_input.length > 0) {
                if ($.trim(phone_input.val()).length == 0) {
                    phone_input.addClass('empty_input');
                    setTimeout(function () {
                        phone_input.removeClass('empty_input');
                    }, 5000);
                    field_error = true;
                }
            }
            if (fullphone_input.length > 0) {
                if ($.trim(fullphone_input.val()).length == 0) {
                    fullphone_input.addClass('empty_input');
                    setTimeout(function () {
                        fullphone_input.removeClass('empty_input');
                    }, 5000);
                    field_error = true;
                }
            }
            if (field_error === true) {
                return false;
            }
            var form_data = new FormData($(this)[0]);
            form_data.delete('summary');
            var file_data_input = $(this).find("input[name='summary']");
            if (file_data_input.prop('files') !== undefined) {
                form_data.append('summary', file_data_input.prop('files')[0]);
            }
            $.ajax({
                type: "POST",
                url: "mail.php",
                cache: false,
                contentType: false,
                processData: false,
                data: form_data,
                success: function (raw_data) {
                    var data = JSON.parse(raw_data);
                    if (data != null && data.success) {
                        console.log(data);
                        $.fancybox.close();
                        $.fancybox({
                            href: '#popup-window-5',
                            tpl: {
                                closeBtn: '<img title="Close" class="popup-window-closbtn" src="img/popup-window-closebtn.png"/>'
                            },
                            'width': '545px',
                        });
                    } else {
                        $.fancybox.close();
                        $.fancybox({
                            href: '#popup-window-6',
                            tpl: {
                                closeBtn: '<img title="Close" class="popup-window-closbtn" src="img/popup-window-closebtn.png"/>'
                            },
                            'width': '545px',
                        });
                    }
                },
                error: function (data) {
                    console.log(data);
                    $.fancybox.close();
                    $.fancybox({
                        href: '#popup-window-6',
                        tpl: {
                            closeBtn: '<img title="Close" class="popup-window-closbtn" src="img/popup-window-closebtn.png"/>'
                        },
                        'width': '545px',
                    });
                }
            });
            return false;
        });