I have been using the non-commercial version of the plugin and as it turned out it does not return the correct http error header as featured. All my not-found pages return code 200 as if they actually exist. This is sad because i like both the simplicity and functionality of the extension but can't use it:( May be its something that you can get in commercial version although featured in both.
Hi, the free version of the Qlue Custom 404 does work, it does generate the correct HTTP status code. It is likely that another extension on your site is causing a conflict. The one thing that you do get with the pro version is great support and I'm sure the team would quickly get to the bottom of this!