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.
We have been using Slingbox with Comcast cable and we just switched to Google Fiber TV. SlingBox is apparently not able to download remote for model GFHD200 TV cable box, so we are not able to use our SlingBox 500. Any suggestions? We tried downloading remote for the 100 model but this does not work either. Thanks for any assistance you can provide!