Dude...I just sat here for 3 hours practically about to put my foot thru the TV. You have to AIM that remote right at the box. I feel like a tool. Glad I seen this thread!
That is sometimes an indication the batteries are weak. Do you know how to check them?
"Remote Settings lets you to see your Xfinity remote control's model number, firmware version and battery level, as well as customize its functionality: