If you change the ISP or your router, you must reset the Slingbox for it to adquire a new IP address and be able to be reached over the Internet.
Feel free to access this link, here you will find the troubleshooting steps that can help you on this situation.
Having similar problem.
My ISP changed today and after that slingbox solo didn't work anymore. (Was working perfectly yesterday..)
I did a reset but no help. The network light just keeps blinking and blinking and no IP is received.
No hardware changes were made.
All the cables are still as they were yesterday.
This is really frustrating...