one simple check is to enable reporting in the plugin or the module instance. If you can see the report on the site, that means jQuery Easy Profiles is enabled on the page you are looking at.
Also, if you are using modules to target specific pages, make sure the position of the module instances corresponds to the position that is set in the plugin. If you did not change it, it should be jqeprofile.
Assuming you have followed the documentation to the letter and since you already have set up the extension on other sites prior to this one, I would suggest you double check your module instance assignments (menu, template...).
Simplify Your Web is not affiliated with or endorsed by The Joomla! Project™ or Open Source Matters. The Joomla!® name and logo is used under a limited license granted by Open Source Matters the trademark holder in the United States and other countries.