Some sections have been renames, so screen customization may lead to such behavior.
(we've identified this issue and will fix it in coming version of the plugin)

Please post here your file /model/custom/Project.php
we'll propose a fix for you.

require_once('_securityCheck.php');
class Project extends ProjectMain {

public $_sec_Description;
public $id;
public $_spe_rf;
public $name;
public $idProjectType;
public $codeType;
public $idClient;
public $idContact;
public $projectCode;
public $contractCode;
public $clientCode;
public $idProject;
public $idCommercial;
public $idSponsor;
public $idResource;
public $penalite;
public $atex;
public $isUnderConstruction;
public $suivideprojet;
public $idUser;
public $creationDate;
public $color;
public $idStatus;
public $idHealth;
public $idQuality;
public $idTrend;
public $idOverallProgress;
public $fixPlanning;
public $done;
public $doneDate;
public $idle;
public $idleDate;
public $cancelled;
public $_lib_cancelled;
public $longitude;
public $latitude;
public $description;
public $objectives;
public $_sec_Progress;
public $ProjectPlanningElement;
public $_sec_Affectations;
public $_spe_affectations;
public $_sec_Versionproject_versions;
public $_VersionProject=array();
public $_sec_Subprojects;
public $_spe_subprojects;
public $_sec_predecessor;
public $_Dependency_Predecessor=array();
public $_sec_successor;
public $_Dependency_Successor=array();
public $_sec_Link;
public $_Link=array();
public $_Attachment=array();
public $_Note=array();
public $sortOrder;
public $_nbColMax=3;
public $lastUpdateDateTime;
public $_sec_Productproject_products;
public $_ProductProject=array();
public $_sec_restrictTypes;
public $_spe_restrictTypes;
public $idOrganization;
public $organizationInherited;
public $organizationElementary;

public static $_customFields=array(
'suivideprojet'
,'idCommercial'
,'penalite'
,'atex'
);

public static $_colCaptionTransposition=array(
"suivideprojet"=>"plgSuivideprojet",
"idCommercial"=>"plgIdCommercial",
"penalite"=>"plgPenalite",
"atex"=>"plgAtex"
);

private static $_fieldsAttributes=array(
"name"=>"required",
"done"=>"nobr",
"idle"=>"nobr",
"sortOrder"=>"hidden",
"codeType"=>"hidden",
"idProjectType"=>"required",
"longitude"=>"hidden",
"latitude"=>"hidden",
"idStatus"=>"required",
"idleDate"=>"nobr",
"cancelled"=>"nobr",
"clientCode"=>"hidden",
"idSponsor"=>"hidden",
"contractCode"=>"required",
"idContact"=>"hidden",
"idHealth"=>"hidden",
"idQuality"=>"hidden",
"idTrend"=>"hidden",
"fixPlanning"=>"",
"description"=>"required",
"projectCode"=>"required",
"suivideprojet"=>"",
"objectives"=>"hidden",
"commercial"=>"",
"idCommercial"=>"required",
"isUnderConstruction"=>"",
"penalite"=>"",
"atex"=>""
);

/** ==========================================================================
* Constructor
* @param $id the id of the object in the database (null if not stored yet)
* @return void
*/
function __construct($id = NULL, $withoutDependentObjects=false) {
parent::__construct($id,$withoutDependentObjects);
}

/** ==========================================================================
* Destructor
* @return void
*/
function __destruct() {
parent::__destruct();
}

/** ==========================================================================
* Return the specific fieldsAttributes
* @return the fieldsAttributes
*/
protected function getStaticFieldsAttributes() {
return array_merge(parent::getStaticFieldsAttributes(),self::$_fieldsAttributes);
}

/** ============================================================================
* Return the specific colCaptionTransposition
* @return the colCaptionTransposition
*/
protected function getStaticColCaptionTransposition($fld=null) {
if (isset(self::$_colCaptionTransposition)) {
return array_merge(parent::getStaticColCaptionTransposition($fld),self::$_colCaptionTransposition);
} else {
return parent::getStaticColCaptionTransposition($fld);
}
}
}
?>

Attached is fixed file.
As your version seems to be old one (before V7.4) be sure to backup your version of the file before installing the new one in /model/custom