Firstly I will presume you are not attempting to break the geo-lock.. you are attempting to use Netflix in the country you live in.
Airport routers do not use upnp .. since apple decided nobody could possibly want to watch anything that isn't on iTunes or play a game on a console etc.
So first thing,, do you have double NAT error. Open the Airport Extreme (AE) in airport utility.. click on its icon and see if there are any errors. If none then please tell me your whole network layout.
1a. Who is your ISP? Are they using IPv6 in your area?
1b. What make and model is your ISP modem?
1c. Is the modem also a router?
2. Is the AE plugged into the modem by ethernet from its WAN port to modem/router LAN port?
3. What device are you using for Netflix? Does it have DNS built in or depends on the router for DNS? If the former did you try using google DNS..?
4. Chromecast has a whole bunch of unique problems.. you should look up chromecast and AE.