Turn on the Brain
Turn on the Brain by pressing the Check button on the Brain.
Turn off the Brain
Turn the Brain off by holding the X button until the screen on the Brain goes black.
Power cycling is the act of restarting a device by turning it off and then back on. This is often done to electronic equipment to reset it if the equipment seems to be malfunctioning.
If the Brain is frozen, and the buttons are not responsive, try removing the VEX IQ Battery and then re-installing it. See this article to see how to install and remove the VEX IQ Battery.