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.
I switched to Verizon Quantum and they installed a new cable box Arris 1100. I installed the Arris 1100 remote from Slingbox and it does not work, I tried so many other remotes and it's driving me crazy. When I called support for my HD Slingbox they told me to check and make sure my cable box is not set to use radio signal (forgot the correct term) and told me to make sure it's set to IR. I do not see any option on the cable box to check that and I also called Verizon and they said it does not have radio signal. What do I do now, throw the Slingbox out? It worked fine on my old cable box.