Hello. If you are getting a blank screen, you are not using the correct URL to access DT Register. If you had manual links setup for a version prior to 2.3.0, then they will no longer work. As of 2.3.0, the whole url structure of DT Register changed. The \"task=listevents\" portion of the url is no longer used and that is most likely why you are getting a blank screen. All you need now to hist the list of events would be this:
http://www.yoursite.com/index.php?option=com_dtregister
This is what you would get from creating a regular component menu item.
Also, be aware that since 2.3, you need to update the DT Register module, mambot/plugin AND the JEvents patch file (if you are using these items) as the link structure changes affected each of them too.