Dahua doesnt check this group anymore, something to do with company policy or blocking in china.
Otherwise I have an installer for the ActiveX version from firmware 2.608, which might help.
You close your browser out, then install the activeX, then open the browser up and it should then work.
details are on this page.
You can test it here:
This is the original WEBREC Dahua Web Service
(basically its like what is on the DVR or camera, but its been modified to run on my website instead)
This is a customized version which auto loads cameras and views.
BUT, your issue might be firmware on the DVR itself.
Hard to say without more information such as what problems you are having.
Rory