Which port are you trying to open? Follow the guide as below to re-check your settings. The page is little different but just for your reference. http://www.tp-link.com/en/faq-72.html

All of us here are users and try to to help each other. If you think it should be but it doesn't, then TP-LINK should make some improvements or they should know it at least. :) C7 is not new any...

I can understand what you are trying to say. Contact TP-LINK support team directly. http://ticket.tp-link.com/index.php?/Tickets/Submit

The dlink cable is in bad quality and you'd better buy another one.

If you have confirmed what I said, submit a ticket here. Maybe support team can remotely access to the web interface and help you to look into it. http://ticket.tp-link.com/index.php?/Tickets/Submit

Where did you place the WA850RE? How many signal lights on it? You have ensure there are 3 at least. If not, you have to move it closer to the router. What's the firmware version of your WA850RE? Try...