Problem using Helper::renderCategoryTree()

[Jlmarin]

I'm trying to develop a module and I need to show the category tree in the admin panel to select multiple categories. I've seen the helper with the "renderCategoryTree" function, but it only shows me the home category.

Any idea what I might be doing wrong?

This is the source code:

public function getContent(){
        if(Tools::isSubmit('procesar')){
            $valueFromPostOrGet = Tools::getValue('email');
            $msg = '<div class="alert alert-info">'.$valueFromPostOrGet.'</div>';
        }

	$url = AdminController::$currentIndex.'&configure='.$this->name.'&token='.Tools::getAdminTokenLite('AdminModules');
	$helper = new Helper();
        $categoryTree = $helper->renderCategoryTree();        
        
        $output .= '
            <div class="row">
                <div class="col-lg-12">
                    <div class="panel col-lg-12">
                        <div class="panel-heading">
                            '.$this->name.'
                        </div>
                            '.$msg.'
                        <form action="'.$url.'" method="post" class="form-horizontal clearfix">
                            '.$categoryTree.'
                            <input type="text" name="email">
                            <input type="submit" name="procesar" value="submit"> 
                        </form>                        
                    </div>
                </div>
            </div>
        ';
        
        return $output;
    }

And this is the result.

 

Thanks.