Sorry that you are experiecing this issue.
Being that there is a HDMI cable in use ( either from cable box to Slingbox or Cable box to TV ), your cable company can randomly send a signal through the HDMI cable and if the signal can sense a Slingbox, it treats it as a recording device and can block the content.
If this is the case, please check out this following article to fix this issue:
- When I connect my set-top box to my TV with HDMI connections, I can't stream video at all using any version of SlingPlayer. Why?
Sling Media Moderation Team