Port forwarding will allow anonymous public traffic to be routed to a specific device in your network. This is the key to allowing remote viewing of your Slingbox. The idea is to direct port 5001 (default) traffic to your Slingbox, so you can watch it over the internet. I believe Actiontec is the router provided by Verizon for the FIOS broadband, here's a site that will assit you. (http://portforward.com/english/routers/port_forwarding/Actiontec/MI-424-WR/SlingBox.htm)
However, if your Slingbox isn't even getting an IP address then its not even participating on the network. I would recommend in performing a factory reset for your Slingbox (http://support.slingmedia.com/get/KB-1000038).