Thank you for posting to the our forums! I do understand that the error message you are receiving is very frustrating and confusing. I did pull up the Slingbox information to make check your settings are correct, and I do show here that the Slingbox is not accessible at this time. This could be causing the error message you are getting. In this situation I would follow the article below. This article will assist you in getting the Slingbox accessible again.
Check out this Article:
Hope everything works out!
The Sling Media Moderation Team