RC66 will only work in IR more on the C31, so pointing at the receiver directly. To reset the remote, put it in the satellite mode, hold mute+select until it blinks (around 3 seconds), enter 981+select. It should blink a few times while resetting. If that doesn't work it may only work with RF mode when an RC73 is programmed and not IR. HR series boxes before Genies only work with IR or RF, not both at the same time, for example. Worse case, RC73 remotes are on eBay or Amazon for nearly the price of shipping alone ($5-$10).