Re-add the $namespace property to the RouteServiceProvider

app/Providers/RouteServiceProvider.php

@@ -10,6 +10,15 @@ use Illuminate\Support\Facades\Route;
 
 class RouteServiceProvider extends ServiceProvider
 {
+    /**
+     * This namespace is applied to your controller routes.
+     *
+     * In addition, it is set as the URL generator's root namespace.
+     *
+     * @var string
+     */
+    protected $namespace = 'App\Http\Controllers';
+
     /**
      * The path to the "home" route for your application.
      *