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 Remember that Arris boxes are built by Motorola
Come back if it that doesn't help either.
Cox (Fairfax, VA) has just releasexd its new Contour 2 playform, and use a new receiver, the Arris XG1v1. This device is not on the list of receivers in the setup menu, making my slingplayer not able to control the box via the remote. Does anyone know of a seting in the current menu that works with this box, or know when they may update the devices list to include this new receiver?