setFieldUpload not allowing to upload file

Grocery CRUD Enterprise
1

Can you guys please help me? When I am trying to upload a file in the edit or add views I am getting an error with the response “This operation is not allowed”

Here is a screenshot of the error including the console:

Capture
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This is the code of my controller:

public function stockcolor()
    {
        $crud = $this->_getGroceryCrudEnterprise();
        $crud->setCsrfTokenName(csrf_token());
        $crud->setCsrfTokenValue(csrf_hash());
        $crud->setTable('stock_color');
        $crud->setSubject('Stock Color', 'Stock Color');
        $crud->setLanguage('Spanish'); 
        $crud->displayAS('name','Stock Color');
        $crud->displayAS('coleccion_id','Colección');
        $crud->displayAS('img_thumbnail','Imagen Miniatura (200x200px)');
        $crud->displayAS('img_banner','Imagen Banner (300x1200px)');
        $crud->displayAS('img_full','Imagen Completa (1920x1080px)');
        $crud->displayAS('img_full2','Imagen Estampados (1920x1080px)');
        $crud->setFieldUpload('img_thumbnail', 'assets/images/estampados', base_url() . '/assets/images/estampados');
        $crud->setFieldUpload('img_banner', 'assets/images/estampados', base_url() . '/assets/images/estampados');
        $crud->setFieldUpload('img_full', 'assets/images/estampados', base_url() . '/assets/images/estampados');
        $crud->setFieldUpload('img_full2', 'assets/images/estampados', base_url() . '/assets/images/estampados');
        $crud->setRelation('coleccion_id','coleccion','name');
        $output = $crud->render();
         /*se agregan las variables para el menú*/
        $coleccion = new ColeccionModel();
        $output -> colecciones = $coleccion->orderBy('name', 'DESC')->findAll(2);//traemos las 2 colecciones más recientes
        $output -> colecciones_viejas = $coleccion->orderBy('name', 'DESC')->findAll(10,2);//traemos las 10 colecciones siguientes
        return $this->_example_output($output);
    }