Apple’s new iPhone 7 models introduce a new solid-state (non-mechanical) Home button which no longer physically depresses but instead is a software-driven sensor. That necessitates a new physical button sequence to hard-reset the device if it stops responding; that happens to be holding the Volume Down and Wake buttons for five seconds.
How to Hard Reset the iPhone 7
Step 1: Press and hold the Lock/Wake button on the right side of your iPhone.
Step 2: At the same time, press and hold down the Volume Down button on the left side while keeping the Lock/Wake button pressed.
Step 3: Keep holding both the buttons until the screen turns black and then switches back on to display the Apple Logo.
Step 4: Wait for a couple of seconds until your iPhone boots up completely and displays the Lock screen.
How to Hard Reset the iPhone 7 (VIDEO)