insert data in database return 404 error in WordPress

Question

I'm trying to insert simple form in database trough ajax without refreshing the page in Wordpress.

For some reason when I click on submit button I've got that the page isn't found - 404 error.

I have added this to my theme function.php

//set_data action 
add_action( 'wp_ajax_set_data', 'my_ajax_foobar_handler' );
add_action( 'wp_ajax_nopriv_set_data', 'my_ajax_foobar_handler' );

function my_ajax_foobar_handler() {

    
    $name = $_POST['name_f'];
    $email = $_POST['email_f'];
    
    $data = array("name" => $name, "email"=>$email);
    global $wpdb;
    global $table_prefix;
    $table = $table_prefix.'contact_form';

    $result = $wpdb->insert($table, array(
    'name' => $name,
    'email' => $email
));

wp_send_json_success($result);

    header("Content-Type: application/json");
    echo json_encode($data);

    

    wp_die();
}

Then I have this in the code snippets for frontend

<?php echo '<form method="POST" id="form">
<table>
<tr>
    <td>name</td>
    <td><input type="text" id="name_field" name="name"></td>
</tr>
<tr>
    <td>email</td>
    <td><input type="email" id="email_field" name="email"></td>
</tr>
<tr>
    
    <td><input type="submit" id="form_submit" name="submit"></td>
</tr>
</table>
</form>';?>



<script>


jQuery('#form').on('submit', function (event) {

        var formData = {
        action: 'set_data',
       name_f: $("#name_field").val(),
       email_f: $("#email_field").val()
      
    };

    


        $.ajax({
            url : '<?php echo admin_url('admin-ajax.php'); ?>',
            data : formData,
            type : 'POST',
            // contentType: "application/json; charset=utf-8",
            dataType : 'json',
            success : function (request) {

                console.log(typeof request);

                console.log(request);

            }
        });

        
    event.preventDefault();
    });
   
 
</script>

<?

I have got this in console log "POST https://website.com/page/?preview_id=2155&preview_nonce=865f9a58ce&preview=true 404 (Not Found)"

on form submit straight goes to the "page not found"