To disable UPnP may help. On its web interface, go to Access Management---UPnP to do that.

TD-W8961ND? Log in its web inteface and try to disable UPnP on Access Management---UPnP page.

How to setup Load Balance to aggregate several WAN links together? http://www.tp-link.com/en/faq-715.html

Did you get a username and password from unifi? There is no WAN IP obtained, right? Any error message in system log?

What's the hardware version of your WR841ND? You may try the method here. If it doens't help, buy a new router....

I realized that I made a mistake after I confirm with TP-LINK support team... The current version of camera control is working with NC200 only... NC220 is not compatible with it but it will work with...