Thanks for your interest in our forums. Sorry to hear that you are no longer able to control the virtual remote after changing your cable box.
When you get a new cable box, you would need to go back through the setup and change your cable box in the settings. If the IR Blasters are in the correct position and still not working, there are a few other steps to try. The article listed below should help you with some further steps.
Hope this helps!
The Sling Moderation Team