If your phone isn't starting, has a black or blank screen or turns on but immediately turns off, try these steps to fix the issue.
Press and hold the Power button for 5-7 seconds or up to 30 seconds.
This restarts (reboots) your phone.
If your phone has a sign-of-life indicator, look for a white light near the top front of the phone. This indicates that the phone is charging but battery is too low to power the screen.
If you're having problems charging, try these troubleshooting steps.