Ajax validation only works when I am connected

Hello !
I am new in Drupal world and I'm trying to use the Drupal From API to create a contact form with Ajax validation.
I'm facing an issues:

• My following form (see below) works well but only when the user is connected as administrator. When I am not logged in as an administrator, ajax validation does not work.

Here is the form I created:

namespace Drupal\dalcom_contact\Form;

use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\HtmlCommand;
use Drupal\Core\Ajax\InvokeCommand;
use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;

class DalcomContactForm extends FormBase {

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'dlcm_cform';
  }

  public function buildForm(array $form, FormStateInterface $form_state, $params = NULL) {

    // Disable caching.
    $form['#cache']['max-age'] = 0;

    // Disable browser HTML5 validation.
    $form['#attributes']['novalidate'] = 'novalidate';

    // This will generate an anchor scroll to the form when submitting.
    $form['#action'] = '#dlcm_cform';

    $form['mail_visitor'] = [
      '#type' => 'email',
      '#placeholder' => t('E-mail*'),
      '#description' => 'Your mail',
      '#required' => TRUE,
      '#ajax' => [
        'callback' => 'Drupal\dalcom_contact\Form\DalcomContactForm::mailValidateCallback',
        'effect' => 'fade',
        'event' => 'change',
        'progress' => [
          'type' => 'throbber',
          'message' => NULL,
        ],
      ],
    ];

    $form['message_visitor'] = [
      '#type' => 'textarea',
      '#placeholder' => t('Message*'),
      '#description' => 'Your message',
      '#required' => TRUE,
      '#ajax' => [
        'callback' => 'Drupal\dalcom_contact\Form\DalcomContactForm::messValidateCallback',
        'effect' => 'fade',
        'event' => 'change',
        'progress' => [
          'type' => 'throbber',
          'message' => NULL,
        ],
      ],
    ];

    $form['accept_box'] = [
      '#type' => 'checkbox',
      '#title' => $this
        ->t('I accept the CME terms of use'),
      '#required' => TRUE,
      '#ajax' => [
        'callback' => 'Drupal\dalcom_contact\Form\DalcomContactForm::acceptboxalidateCallback',
        'effect' => 'fade',
        'event' => 'change',
        'progress' => [
          'type' => 'throbber',
          'message' => NULL,
        ],
      ],
    ];

    $form['candidate_copy'] = [
      '#type' => 'checkbox',
      '#title' => t('Send me a copy of my message.'),
    ];

    $form['actions']['#type'] = 'actions';

    $form['actions']['submit'] = [
      '#type' => 'button',
      '#value' => $this->t('Send'),
      '#ajax' => [
        'event' => 'click',
        'progress' => [
          'type' => 'throbber',
          'message' => 'Sending...',
        ],

      ],
    ];

    $form['#theme'] = 'dalcom_contact_theme';

    return $form;
  }

  public function submitForm(array &$form, FormStateInterface $form_state) {
    foreach ($form_state->getValues() as $key => $value) {
      drupal_set_message($key . ': ' . $value);
    }
  }

  public function mailValidateCallback(array &$form, FormStateInterface $form_state) {
    $ajax_response = new AjaxResponse();

    if (!$form_state->getValue('mail_visitor') || empty($form_state->getValue('mail_visitor'))) {
      $text = 'No email registered';
      $color = 'red';
    }
    elseif (!filter_var($form_state->getValue('mail_visitor'), FILTER_VALIDATE_EMAIL)) {
      $text = 'Invalid email address';
      $color = 'red';
    }
    else {
      $text = 'Valid mail';
      $color = 'green';
    }

    $ajax_response->addCommand(new HtmlCommand('#edit-mail-visitor--description', $text));

    $ajax_response->addCommand(new InvokeCommand('#edit-mail-visitor--description', 'css', ['color', $color]));

    return $ajax_response;
  }

  public function messValidateCallback(array &$form, FormStateInterface $form_state) {
    $ajax_response = new AjaxResponse();

    if (!$form_state->getValue('message_visitor') || empty($form_state->getValue('message_visitor'))) {
      $text = 'No messages written';
      $color = 'red';
    }
    elseif (strlen($form_state->getValue('message_visitor')) < 6) {
      $text = 'At least 7 characters';
      $color = 'red';
    }
    else {
      $text = 'Messages written';
      $color = 'green';
    }

    $ajax_response->addCommand(new HtmlCommand('#edit-message-visitor--description', $text));

    $ajax_response->addCommand(new InvokeCommand('#edit-message-visitor--description', 'css', ['color', $color]));

    return $ajax_response;
  }

  public function acceptboxValidateCallback(array &$form, FormStateInterface $form_state) {
    $ajax_response = new AjaxResponse();

    if (empty($form_state->getValue('accept-box'))) {
      $text = 'You must accept our termes of use to continue';
      $color = 'red';
    }

    $ajax_response->addCommand(new HtmlCommand('#edit-accept-box--description', $text));

    $ajax_response->addCommand(new InvokeCommand('#edit-accept-box--description', 'css', ['color', $color]));

    return $ajax_response;
  }

}

It works very well. But Ajax validation only works when I am connected. When I am not logged in as an administrator, it does not work.

Here is the block to display the form in my footer.

namespace Drupal\dalcom_contact_block\Plugin\Block;

use Drupal\Core\Block\BlockBase;
use Drupal\Core\Form\FormInterface;

/**
 * Provides a 'dalcom contact' block.
 *
 * @Block(
 *   id = "dalcom_contact_block",
 *   admin_label = @Translation("Dalcom Contact Block"),
 *   category = @Translation("Block du formulaire Dalcom Contact")
 * )
 */
class DalcomContactBlock extends BlockBase {

  /**
   * {@inheritdoc}
   */
  public function build() {
    $form = \Drupal::formBuilder()->getForm('\Drupal\dalcom_contact\Form\DalcomContactForm');
    return $form;
  }
}

Here is the module.routing.yml file

dalcom_contact.form:
  path: '/contact-us.html'
  defaults:
    _title: 'Contact Us'
    _form: 'Drupal\dalcom_contact\Form\DalcomContactForm'
  requirements:
    _permission: 'access content'

block.info.yml

name: Dalcom Contact Block
type: module
description: Block du formulaire Dalcom Contact.
core: 8.x
package: Custom
dependencies:
- node
- block

Does anyone have any idea what could cause this? Please help me.