Group field not showing in metabox

Hi,
I'm new to the premium plugins, and I tried that night to implement a group field using the doc, but it looks like it won't appear in admin.
Below is my code. The other fields of the metabox are showing, and after a few tests, it looks like the group field class is loaded, but the html method is never triggered.

meta_boxes[] = array(
		'id'         => 'infos_supp_adherent',
		'title'      => "Informations sur l'Adhérent",
		'post_types' => array( 'adherent' ),
		'fields' => array(
			array(
				'name' => "Nom",
				'id' => $prefix . "adherent_nom",
				"type" => "text", 
				"required" => true,
				"clone" => false
				),
			array(
				'name' => "Prénom",
				'id' => $prefix . "adherent_prenom",
				"type" => "text", 
				"required" => true,
				"clone" => false
				),
			array(
				'name' => "Date de Naissance",
				'id' => $prefix . "adherent_naissance",
				"type" => "date", 
				"required" => true,
				"clone" => false,
				"dateFormat" => "dd/mm/yy"
				),
			),
			array(
				'name' => "Coordonnées",
				'id' => $prefix . "adherent_coordonnees",
				'type' => 'group',
				//'required' => true,
				'clone' => true,
				'fields' => array(
					
					array(
						'name' => 'Information',
						'id' => $prefix . "adherent_coordonnees_valeur",
						'type' => 'text',
						'required' => true,
						'clonable' => false,
					)
				)
			)
		);