yii2 - Yii::$app->session->setFlash() is not working -

following code in sitecontroller works fine echo, not yii-method setflash(). maybe, have reconfigure config-file(main-local.php)? other ideas how keep setflash() doing job?

   public function actionscript() { //a new method, programmed thomas kipp         $model = new myscriptform();         $filename = 'file';         $uploadpath = yii::getalias('@uploading');          if (isset($_files[$filename])) {             $file = \yii\web\uploadedfile::getinstancebyname($filename);              if ($file->saveas($uploadpath . '/' . $file->name)) {                 echo"<script>alert('hallo');</script>";                 //echo \yii\helpers\json::encode($file);             }         }         if ($model->load(yii::$app->request->post()) && $model->validate()) {             $model->fileimage = uploadedfile::getinstance($model, 'fileimage');             $model->avatar = uploadedfile::getinstances($model, 'avatar');             if ($model->fileimage) {                 yii::$app->session->setflash('success', 'file has been uploaded');                 echo "<font size='4'><br><br><br><center>file <font color='red'> "                 . "$model->fileimage<font color='black'> uploaded."                 . "<br>it's available in folder 'uploadedfiles' </font></font color></center>";                 $model->fileimage->saveas(yii::getalias('@uploadedfilesdir/' . $model->fileimage->basename . '.' . $model->fileimage->extension));             } else {                 yii::$app->session->setflash('error', 'there has nothing uploaded');                 echo"<font size='4'><br><br><br><center>no upload-file selected.<br>"                 . "nothing moved folder 'uploadedfiles'</font></center>";             }             if ($model->avatar) {                 $counter = 0;                 foreach ($model->avatar $avatar) {                     yii::$app->session->setflash('success', 'avatar has been uploaded');                     echo "<font size='4'><br><center>file <font color='red'> "                     . "$avatar<font color='black'> uploaded."                     . "<br>it's available in folder 'uploadedfiles' </font></font color></center>";                     $avatar->saveas(yii::getalias('@uploadedfilesdir/' . $avatar->basename . $counter . '.' . $avatar->extension));                     $counter++;                 }             } else {                 yii::$app->session->setflash('error', 'there has nothing uploaded');                 echo"<font size='4'><br><center>no upload-file selected.<br>"                 . "nothing moved folder 'uploadedfiles' </font></center>";             }             return $this->render('myscript', ['model' => $model]);         } else {             return $this->render('myscript_formular', ['model' => $model]);         }     } 

once have assign value eg:

 yii::$app->session->setflash('error', 'there has nothing uploaded'); 

be sure in view eg: myscript.php echo value setted

<?= yii::$app->session->getflash('error'); ?>