2 routers can cause you the problem, be sure that when you try to setup the slingbox you are using a pc/laptop connected to the same router where the slingbox is attached and disable any firewall/antivirus the moment you try to run the setup
Also to confirm that the 350 is visible from your router, check the list of attached devices and verify if a mac address starts with 00:0D thats a slingbox
The slingbox is setup behind two routers. Port forwarding is enabled on both. I have confirmed that a connection from the Internet (not my local network) to port 5201 is accepted. Internally, the Slingbox also accepts connections on ports 22 and 8888, but these ports are not forwarded from the Internet.
Nevertheless, when I goto Slingbox.com/getstarted, I cannot get it to find the Slingbox. When I goto whatismyip.com, write down the IP, goto a machine outside my local network, I can connect to that IP on port 5201.
I have factory reset the Slingbox several times while on the network. I have tried visiting Slingbox.com with multiple browsers and multiple computers, to no avail.
Please help! I will share my IP privately if you can better diagnose.