Help with first custom module

Hey! I'm extremely new to Drupal development and have the following code:

kay_user.module:

<?php

/**
* @file
* Task 1 - only ask for email address and change username label to Full Name
*/

use Drupal\Core\Form\FormStateInterface;

/**
* Task 1 - change label from username to Full Name and asks for email
* Implements hook_form_alter().
*/
function kay_user_form_alter(&$form, Drupal\Core\Form\FormStateInterface $form_state, $form_id){
//attempting to print with dsm
dpm(form_id);
 
if ($form_id == 'user_login_form') {
//- change label for username input
$form['name']['#title'] = t('Full Name');

$form['name']['#title'] = t('Email address.');
$form['name']['#description'] = t('Enter your email address');
$form['name']['#element_validate'][] = 'kay_user_user_login_validate'
}
}

/**
* Form element validation handler for the user login form.
*
* Allows users to authenticate by email
*/
function kay_user_user_login_validate($form, FormStateInterface $form_state) {
$name_input = $form_state->getValue('name');

// Try loading by email.
if ($user = user_load_by_mail($name_input)) {

// Set the username for further validation.
$form_state->setValue('name', $user->getAccountName());
return TRUE;
}
return FALSE;
}

kay_user.info.yml:

name: Kay User
description: Edits login and registration forms
package: Custom

type: module
core: 8.x
version: 1.0

I've checked that the module is enabled, but I don't get any response when I try to run this. It also never prints the form id from the dpm(form_id) command. Any thoughts?