Thank you for posting to the forums! I understand that you changed the wifi router inside the house and now the Slingbox is not found on the network. I would be happy to help! Basically what you will need to do is reset the Slingbox so that it can obtain the new IP address for the new wifi router.
Here is an article that I suggest you try.
After you complete this article you will need to reconfigure the Slingbox on setup.slingbox.com.
The Sling Moderation Team