I cannot use uPnP or cannot change my router settings
Warframe uses UDP ports 4950 and 4955 & the TCP port range 6695 - 6699. Your router needs to let traffic on those ports through to your PC. For your convenience these ports and your local IP address are shown in the network analysis dialog.
The instructions for forwarding ports on your router vary by manufacturer and model; please consult your router’s documentation or the manufacturers support site for details on how to correctly forward these ports to your PC.