Reboot your iPhone 7 or perform a force restart

Try to turn your iPhone back on after connecting it to an outlet and allowing it to charge for a few minutes. To do so, hold down the Sleep/Wake (Power) button until you see the Apple logo on the screen.

You might also try forcing your iPhone 7 to restart. To force a restart, simultaneously press and hold the Sleep/Wake and Volume Down buttons for at least 10 seconds. Release both buttons when you see the Apple logo.

The contents of your iPhone will not be erased if you force it to restart.

The contents of your iPhone will not be erased if you force it to restart. As a result, it's a highly suggested remedy, especially if your iPhone's screen is blank or its buttons aren't functioning.