Thanks for using our forums. Sorry to hear you are getting an error message when trying to view the Slingbox. The Slingbox, however, wouldn't be giving an error message that states it isn't authorized. This sounds like an error within your TV Service. If it was an issue with the Slingbox, you would get no video signal at all. You would more than likely want to reset your cable box at this point and see if it fixes the issue, if not, you will want to contact your cable company back to see where this issue is coming from.
Hope this helps,
The Sling Moderation Team