Thanks for posting in the Slingbox Answers Forum! I apologize for the inconvenience of not being able to connect to your Slingbox PRO-HD after changing the router that it is connected to.
In order for the Slingbox to get a connection from the new router, it will need to be reconfigured. To do this, you will need to hard reset the Slingbox to factory settings, then go through the online setup at setup.slingbox.com.
Below is a link to an article from our support site that explains how to reset your Slingbox to factory settings:
Hope this helps!
The Sling Moderation Team