My CISCO home router was unreliable using uPNP. It would work for a few days and then fail. I had to power cycle the router. I figured it was because I was running other instances which would "fight" over the port... but maybe its a uPNP bug or timeout.
You could try port forwarding. Its pretty easy if you can log into your router. To be sure it works, you need to both assign an explicit IP address for your compter in the DHCP configuration (you basically tell it "whenever you see this MAC address (which you can find in the settings on your computer), assign this IP". And then you forward port 8333 to the IP you picked.