Cron Tasks are not executed if URL rewriting in ACP is enabled.
The generated cron image links to non existing site and generate a http 404.
Fatal error: Uncaught Symfony\Component\Routing\Exception\MissingMandatoryParametersException: Some mandatory parameters are missing ("cron_type") to generate a URL for route "phpbb_cron_run"...
Error Log from Apache 2.4:
Negotiation: discovered file(s) matching request: /path/to/phpbb33/cron (None could be negotiated).
Add the following line into the .htaccess in the phpBB Forum root: