From the Help menu
Press A on your Rogers Xfinity Voice Remote.
Highlight Restart. Press OK.
Highlight Restart and press OK again.
It may take a few moments for the Rogers Xfinity Entertainment Box to reboot.
From the Rogers Xfinity Entertainment Box
Unplug the power cord from the back of the box.
Wait for 10 seconds and plug it back in.
The Rogers Xfinity Entertainment Box should automatically reboot.