This sounds like you are getting this message on your computer when you are trying to watch your Slingbox, is that correct?
If so, what the issue is when the modem/router in the home gets replaced, the Slingbox retains the previous modem/router network configuration. To fix this a Hard Rest will have to be done to the Slingbox.
The article below goes into further detail on how to do a Hard Rest:
Do not forget after the reset is done, go to Setup on Slingbox,com to reset up the Slingbox.
Hope this helps!!
Sling Media Moderation Team