Before using the built-in DVR DDNS service, please make sure all ports for standalone DVR are open. By default these are 80, 9010, 9011
We also recommend assigning a static IP to the DVR using the DVR set-up or by setting up DHCP reservation in the router.
Then go back to DVR menu -> DDNS -> Create a domain name -> Click on Check
DVR will pop up a message "The domain can be used", if the port is not open, DVR will not pop up any message.