Andrew found the solution. This probably happened because the IP number changed that he had been using.  ”Launch the Slingplayer app from within the same network that the Slingbox is on.

If you’re using the app on a Macintosh, from the Slingbox menu, select Get Info. Choose the configuration tab, then select the Change Network Settings button. Run the setup.

If you’re using the app on a PC, from the Settings menue, select Setup Assistant and run the entire setup.

Then, from outside this network you should be able to hit that box via any Slingbox app.”