Since your Slingbox can't be located on your network, the issue might be caused by the connections that your are using for your devices or an Anti Virus software blocking the application.
I encourage you to check the instructions on this link and complete the troubleshooting steps. If the issue remains, please include more information on how is your Slingbox connected to the router and which softwares are installed on your computer.
I hope that helps.
The Slingbox Answers Forum Moderation Team