When I "Enable URL Optimization" in sh404 (basically turn it on), the browser displays an empty white screen.

Maximum Joomla Error Reporting shows:
Fatal error: Call to undefined method Sh404sefFactory::getConfig() in /public_html/components/com_payplans/sef_ext/com_payplans.php on line 14

That line is

$sefConfig = & Sh404sefFactory::getConfig();

What is wrong?

Thank you