On this page Guide to the LiveAPI System - The header() Method - Software Development Kit - cPanel Documentation it says:
How do you print the header/footer of paper_lantern theme in a php file on cPanel/WHM 11.44?Note:
This method is available in cPanel & WHM version 11.46 and later. The app_key parameter is only available in cPanel & WHM version 11.52 and later. This method is only compatible with cPanel's Paper Lantern theme.