Надеюсь теперь работает

app/Http/Controllers/YoutubeDownloadController.php

@@ -30,7 +30,7 @@ class YoutubeDownloadController extends Controller
                 $videotitle = $video->getFile()->getFilename(); // Will return Phonebloks
                 // $video->getFile(); // \SplFileInfo instance of downloaded file
                 //$file_path = public_path('/downloads/'.$videotitle);
-                return redirect('/download/'.$videotitle);
+                return redirect()->route('/download/'.$videotitle);
                 //return response()->download($file_path);
             }
         }