I understand the cable box model you have which is from the X1 Platform XiD-c from Xfinity is not listed on our database.
When you get the option that asks to (Search for manufacturer or Pick from the list)
you need to select Search and type "X1 XR5"
This is the XR5 remote which comes along with the cable box you have and should be able to control your cable box.
Hope this helps!
Sling Media Technical Support