Had Greg look over it for syntax and typos and to confirm settings in php.ini and config.inc.php were correct. Spent a couple of hours reviewing the plugin code. Disabled a bunch of other plugins to see if there was conflict. Searched entire codebase for other plugins with listener for same event as used by sample plugin to see if they were swallowing the event. No luck. Shawn sat in for a bit and we tested various things by inserting die() statements to see exactly which bits of code were being executed and which weren't. Confirmed that the plugin is being registered, and that the event is never caught. Also checked the page throwing the event to make sure it was throwing exactly the event that we're looking for. No luck. More searching on the user forum indicates that I have to include an entry into one of the tables in the database. That information is usually stored in an xml file in the plugin, but not yet sure how OJS gets that information from the xml file into the db. That's next