To perform a hard reset on the SkyBell Version 2 (SkyBell Classic):
Hold the SkyBell's physical push-button for about 55 seconds. You will want to watch the L.E.D. light while holding the button which will go from slow blinking to a fast red blinking at around the 45 second mark then to an even faster flickering/strobe-like red light. Once it begins strobing red you will release the button. The SkyBell will then reset itself for a few seconds and return to a Solid red or a slow blinking red.
DO NOT PERFORM A HARD RESET ON A SKYBELL VERSION 1 AT ANY TIME, this could prevent the version 1 from ever being able to sync again.