I assume you have already done a proper Forum Search for your model number in case other people have already answered your question ?
If so and that didn't help then check out this thread: https://community.sling.com/message/10363#10363
Come back if it that doesn't help either.
My son set up the Slimgbox before moving overseas to work. I'm not the most technologically skilled person in the world. We recently changed our Cable service for that TV and went to a smaller, cheaper box from Comcast. It resulted in a new Remote that they now commonly use. Since I'm here, I'm the one trying to make it work. He gets a picture but can't change channels.
It seems, from a Google Search going back a year that people are having Slingbox problems with it and I didn't find a solution. I did not find that Remote on this list of custom remotes you sent me the link for.
This seems crazy that Slingbox doesn't list/support a very common xfinity remote! Any help is still appreciated.
Sent from my iPad