I'm sorry to hear you are unable to view your Slingbox after completing the setup process. The No Video Signal could be caused by a couple different things. Please check out the link below for step by step troubleshooting for this particular issue:
Hope this helps!
The Sling Moderation Team
This is the way I solved the problem for me. I connected the HDMI out of my pvr directly to my tv, like before installing the slingbox. I just connected the component output of my pvr to the slingbox. The slingplayer on my nexus 7 tablet and on my Samsung S3 work fine with this setup. Hope that help !