Extended model not saving additional fields

PHP Code:

declare(strict_types=1);

namespace App\Models;

use CodeIgniter\Shield\Models\UserModel as ShieldUserModel;

class UserModel extends ShieldUserModel
{
    protected function initialize(): void
    {
        parent::initialize();

        $this->allowedFields = [
            ...$this->allowedFields,
            'first_name',
            'middle_initial',
            'last_name',
        ];
    }
}

PHP Code:

<!-- First Name -->
<div class="form-floating mb-2">
    <input type="text" class="form-control" id="floatingFirstnameInput" name="first_name"
        inputmode="text" autocomplete="first_name" placeholder="<?= lang('Auth.first_name') ?>"
        value="<?= old('first_name') ?>" required>
    <label for="floatingFirstnameInput">
        <?= lang('Auth.first_name') ?>
    </label>
</div>

<!-- Middle Initial -->
<div class="form-floating mb-2">
     <input type="text" class="form-control" id="floatingMiddleinitialInput" name="middle_initial"
           inputmode="text" autocomplete="middle_initial" placeholder="<?= lang('Auth.middle_initial') ?>"
           value="<?= old('middle_initial') ?>">
     <label for="floatingMiddleinitialInput">
         <?= lang('Auth.middle_initial') ?>
     </label>
</div>

<!-- Last Name -->
<div class="form-floating mb-4">
    <input type="text" class="form-control" id="floatingLastnameInput" name="last_name"
        inputmode="text" autocomplete="last_name" placeholder="<?= lang('Auth.last_name') ?>"
        value="<?= old('last_name') ?>" required>
    <label for="floatingLastnameInput">
        <?= lang('Auth.last_name') ?>
    </label>
</div>