What version of DT Register are you using? Make sure you have the latest build, which would be 2.5.4a. There was an attendee list issue in a recent release that was already fixed.
We actually just release 2.5.5 so go ahead and upgrade. Then, also check your settings as some people miss this one detail for showing the attendees.
Not only do you need to setup the configuration for "View Registrants", but in EACH event, you need to enable this if you want to use it. It is purposely setup PER EVENT. In Event Management, you'll see a parameter "Show Attendee's Button: Hide/Show". Set this to "Show" if you want to see the attendees for that event.