If your screen is black or frozen
First, try to force your device to restart.Forcing your device to restart won't erase the content currently on your device. You can force your device to restart even if your screen is black or your buttons aren't responding.
To force restart an iPhone 7 or iPhone 7 Plus: Press and hold both the Sleep/Wake and Volume Down buttons for at least ten seconds, until you see the Apple logo.
To force restart an iPhone 6s and earlier, iPad, or iPod touch: Press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.
If your device still won't turn on or start up
Plug in your device and let it charge for up to one hour.
After a few minutes, you should see the charging screen.
If you don't see the charging screen within an hour, or you see the connect to power screen, check the jack, USB cable, and power adapter. Make sure that...