Mevo Boost will not charge your camera or provide any its other features unless it is powered on.
To turn on the device, press and hold the button on the back of the unit under the outer ring lock until the white LED's start rotating on and off.
To turn off the Boost, press and hold the same button until a single LED turns on and the LED's rotate on and off for a moment. When the LED's are all off, the Boost is off.
