This plugin needs to be loaded before the plugin which code you want to display. So adjust order in the plugin manager (filter on 'content'), make sure the order has a number (not '0').
This project is an official fork of SPIC for Joomla 1.5: http://extensions.joomla.org/extensions/edition/code-display/11369 from MediaEventi:
This is a great plugin and very useful for displaying Joomla or any other code within an article without the Joomla application trying to render it!
I have seen many tutorials, for example on the loadmodule syntax, where the example pseudo-code provided is rendered or is missing, making the information useless.
It is a shame this extension is so little appreciated
A note on usage: If you need to format your code, make sure to place the formatting code before and after the plugin embed tag, otherwise the formatting code will also appear un-rendered as text.