Kentico 12 MVC Custom scheduled task

Hi all, Following the instructions given here: https://docs.xperience.io/k12sp/configuring-kentico/scheduling-tasks/scheduling-custom-tasks I made a simple task which I want to register as a scheduled task in the kentico scheduled tasks module but my namespace and task name don't appear in the Task Provider assembly name or class. Even when I copy the namespace from the code and the class name it gives me an error @Invalid assembly or class name selected.@ How do I get my namespace to appear here and register this scheduled task ? Regards