Error when downloading certificate

After finishing a course, the certificate can't be downloaded. Even using the default certificate or creating a new one still throws an error.

Error:
Symfony\Component\Routing\Exception\ResourceNotFoundException: No routes found for "/certificate/group/2/pdf" in Drupal\Core\Routing\Router->matchRequest() (line 124 of core\lib\Drupal\Core\Routing\Router.php)."