Thank you for posting in the forums! I'm sorry to hear you are not getting all of your channel listings in the channel guide.
I would recommend hard resetting your Slingbox to factory settings. After you do this you will have to go through the setup again. Feel free to reply if the issue persists.
Below is a link to an article that explains how to reset your Slingbox to factory settings:
Hope this helps!
The Sling Moderation Team