>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3394085. --> Reported by: [bramvandenbulcke](https://www.drupal.org/user/2456648) Related to !317 >>> <p>I wanted to test the new experimental sidebar navigation but I got an error. The website was unreachable; I had to use drush to change the admin theme. </p> <p>The error was: </p> <pre>Symfony\Component\Routing\Exception\RouteNotFoundException: Route "help.main" does not exist. in Drupal\Core\Routing\RouteProvider-&gt;getRouteByName() (line 206 of /Users/Bram/Sites/website/web/core/lib/Drupal/Core/Routing/RouteProvider.php).</pre><p>I had no Help region in my custom theme. When creating a Help region, the same error was shown. </p>