The Hushh has a child-safe setting to lock it in an off or on position safe from small hands who may try to play with it while in use. If the control buttons on your Hushh unit appear to be non-responsive, the child lock might be engaged. To remedy this, press the "Power" and "Select" buttons at the same time and hold for a few seconds until you see the indicator light blink three times. After you do this step, try to adjust the volume to see if you've unlocked the unit.
If your sound machine still won’t turn off, please see this article link.