dynamic update not work

i generate my model using phalcon devtools, my model code like this:

public function initialize()
{
    parent::initialize();
    $this->useDynamicUpdate(true);
}

    public function columnMap()
{
    return [
        'id' => 'id',
        'first_name' => 'firstName',
        'last_name' => 'lastName',
        'login_name' => 'loginName',
        'email' => 'email',
        'password' => 'password',
        'sex' => 'sex',
        'birthday' => 'birthday',
        'activation_code' => 'activationCode',
        'persist_code' => 'persistCode',
        'reset_password_code' => 'resetPasswordCode',
        'permissions' => 'permissions',
        'is_activated' => 'isActivated',
        'activated_at' => 'activatedAt',
        'last_login' => 'lastLogin',
        'is_vip' => 'isVip',
        'created_at' => 'createdAt',
        'updated_at' => 'updatedAt'
    ];
}

my website dynamic update not work.