Thank you for utilizing our online answer forums. We apologize that you are experiencing an issue with you Slingbox not controlling the cable box. With this issue you would need to have someone at the Slingbox location check the position of the IR emitter(if being used), if the IR emitter is not being used I recommend you plug in the IR emitter cable and see if that allows you to control the cable box. The IR emitter cable is a cable that we have provided with the Slingbox, it will have a pyramid on one end. If you need to plug in this cable, the Pyramid needs to be in front of the cable box about 1 to 3 inches away. If you are using the IR emitter cable, and the position is correct. Then you will need to do a digital camera test to see if the IR emitter is still working. Below I have listed you a few articles that will help you with the digital camera test and position of the IR emitter.
As promised here are those links:
Hope this helps
Sling Media Moderation Team.