Hi JB
Have not enabled DDNS for my NVR on HikConnect, so I cannot know.
I did enable once, disabled Advanced firewall for my Internet provider, opened 2 ports (8000 and 80) for my NVR's ip address and then tried remotely working on iVMS doing settings which was OK. Then I restored back everything and disabled DDNS on HikConnect.
What I did not check was, if I enabled Virtual Host there I could also do settings on my cameras.