Export Excel generate error... using http://www.maatwebsite.nl/laravel-excel/ lib

Please help me, i keep receiving this error when using the library to export...

Code Excel::create('New file', function($excel) {

            $excel->sheet('New sheet', function($sheet) {

                $pins = $this->excel_param;

                $sheet->loadView('admin.pin_to_excel', compact('pins'));

            });

        })->download('xlsx');

Error ErrorException in CssParser.php line 100: simplexml_import_dom(): Invalid Nodetype to import

Please what its missing???