第二次单击按钮时不显示AJAX响应

I have a simple login form in which I have passed the values through AJAX call. The problem is when I enter wrong email or password for first time, It displays me the error message. 2nd time if I enter something wrong it does not show the error. Where am I doing wrong any suggestions/help please.

Form

<?php
if (isset($_SESSION['login_email']) && !empty($_SESSION['login_email'])) {
    //header('Location:profile.php');
?>
<script> location.replace("profile.php"); </script>
<?php
} else {
?>
  <div class="login_form">
    <h1 class="login_heading">Login</h1>
    <div class="alert-error"></div>
    <div class="alert-success"></div>
    <div class="login">
      <form method="post" action="">
        <label >Email</label>
        <input class="inputs_login" type="email" name="email" id="email" placeholder="email" >
        <label>Password</label>
        <input class="inputs_login" type="password" name="password" id="password" placeholder="password"><br>
        <input type="button" name="login_submit" id="login_submit" value="login">
      </form>
    </div>
  </div>
<?php
}
?>

Ajax

<script>
  $(document).ready(function() {
    $('#login_submit').click(function(e){
      //e.preventDefault();
      var  email = $("#email").val(),
          password = $("#password").val();
      var proceed = true;
      if(proceed){
        post_data= { 'Email': email, 'Password': password};
        $.post('login_index.php', post_data, function(response){
          //load json data from server and output message
          if(response.type == 'error')
          {
            output=$('.alert-error').html(response.text);
          }else{
            location.href="profile.php";
          }
          $(".alert-error").delay(3200).fadeOut(300);
        }, 'json');
      }
    });
  });
</script>

php

<?php
include "db/db.php";
session_start();
if ($_POST) {
    if (!isset($_SERVER['HTTP_X_REQUESTED_WITH']) AND strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) != 'xmlhttprequest') {

        //exit script outputting json data
        $output = json_encode(array(
            'type' => 'error',
            'text' => 'Request must come from Ajax'
        ));

        die($output);
    }
    if (isset($_POST['Email']) && isset($_POST['Password'])) {
        $email = filter_var($_POST["Email"], FILTER_SANITIZE_STRING);
        $pwd   = filter_var($_POST["Password"], FILTER_SANITIZE_STRING);
        $query = mysqli_query($con, "select * from customers where email='$email' and password='$pwd'");
        $count = mysqli_num_rows($query);
        $row   = mysqli_fetch_array($query, MYSQLI_ASSOC);
        if ($row) {

            $_SESSION['login_email'] = $row['email'];
            $output                  = json_encode(array(
                'type' => 'message',
                'text' => 'Hi ' . $email . ' You are successfully login'
            ));
            die($output);

        } else {
            $output = json_encode(array(
                'type' => 'error',
                'text' => 'Could not Login! Please check your email/password OR <a href="index.php?page=register_account">REGISTER FREE ACCOUNT</a> .'
            ));
            die($output);
        }
    }

}
?>